Which of the following statements is TRUE about major histocompatibility (MHC) proteins? a. All cells produce both class I and class II MHC proteins. b. Class I MHC are secreted while class II is on the cytoplasmic membrane. c. Class I and II MHC proteins are on the cytoplasmic membrane. d. All cells produce class II MHC proteins.

Answers

Answer 1

Statement c. is TRUE about major histocompatibility (MHC) proteins. Both class I and class II MHC proteins are present on the cytoplasmic membrane.

Major histocompatibility complex (MHC) proteins play a crucial role in the immune system by presenting antigens to T cells. Regarding the statements provided, statement c. is correct. Both class I and class II MHC proteins are found on the cytoplasmic membrane.

Class I MHC proteins are expressed on the surface of almost all nucleated cells and are involved in presenting antigens derived from intracellular pathogens. They present these antigens to cytotoxic T cells, which helps initiate a cellular immune response.

Class II MHC proteins, on the other hand, are primarily expressed on the surface of antigen-presenting cells such as macrophages, dendritic cells, and B cells. They are involved in presenting antigens derived from extracellular pathogens. Class II MHC proteins present these antigens to helper T cells, which stimulate the immune response.

In summary, both class I and class II MHC proteins are located on the cytoplasmic membrane, with class I MHC proteins present on most nucleated cells and class II MHC proteins mainly found on antigen-presenting cells

learn more about cells click here;

brainly.com/question/19853211

#SPJ11


Related Questions

What places has a Temperate Deciduous Forest biome? (city/ country)

Answers

Answer:

Temperate deciduous forests can be found in the eastern part of the United States and Canada, most of Europe and parts of China and Japan.

Explanation:

A que altura debe moverse un costal de cemento de 50kg para asegurar que su energía potencial sea de 10,500 j?

Answers

Answer:

21 m

Explanation:

La energía potencial de un cuerpo es la energía que posee el cuerpo en virtud de su posición.

La energía potencial se da como;

E = mgh

Dónde;

m = masa del cuerpo

g = aceleración por gravedad

h = altura del cuerpo

Aquí necesitamos obtener la altura del cuerpo.

h = E / mg

h = 10500/50 * 10

h = 21 m

Please helpp
I don't understand this at all

Answers

Ok so lemme help u.
Every A becomes T and every C becomes G vice versa.

If you’re doing MRNA
Then instead of T you write U

Compare marshes, swamps, and bogs.​

Answers

Marshes, swamps, and bogs are all types of wetlands. This means that their soil can be saturated either permanently or seasonally. As wetlands, they are all characterized by high levels of biodiversity. Swamps tend to have a larger proportion of surface water than marshes and, in North America, are characterized by the presence of trees. Bogs have acidic groundwater as a result of their surface water resulting mainly from precipitation

Answer:

Marshes: Have extremely good ability to support grasses, reeds, flowers, and insects due to their high nutrient soil. They usually are around lakes/rivers/and other bodies of water. They are frequently covered in water however not always covered in water.

Swamps: Have extremely good ability to support wood like plants, trees. They are also permanently covered/submerged in water all year around.

Bogs: Basically they are a gravesite of a dead plant life. When a lake fails to support itself it turns into a bog, its plant life dies off and will start rising to the top creating almost a film. However even though the plant life dies the insects, reptiles, and Amphibians thrive.

Explanation:

Hope this helps!

Please help and thank you whoever you are

Answers

i believe it’s 2. the suns radiation provides heat to the earth sorry if i am wrong

Explain why it is important to study ocean microbes with regard to the biosphere.

Answers

Answer:

Studying marine microbes is very important because it controls the major biogeochemical cycles that balance the Earth's biosphere.

Explanation:

Answer:

They are also major pillars of the biosphere. Their unique metabolisms allow marine microbes to carry out many steps of the biogeochemical cycles that other organisms are unable to complete. The smooth functioning of these cycles is necessary for life to continue on earth.

Explanation:

What is the function of Stomata?

Answers

Answer: Stomata, the small pores on the surfaces of leaves and stalks, regulate the flow of gases in and out of leaves and thus plants as a whole. Stomata are composed of a pair of specialized epidermal cells referred to as guard cells (Figure 3). Stomata regulate gas exchange between the plant and environment and control of water loss by changing the size of the stomatal pore.

Explanation:

6. Which of the following is true during telophase?
a. The nuclear membrane has disappeared.
b. The cell membrane begins to form cleavage furrow at the center.
C. Two new cells are formed with the same number of chromosomes as the parent cell.
d. The centromere of each chromosome divides and pulls them by the spindle fibers toward
the end of the cell.

Answers

Explanation:

what is the name of this website or the book

Vacuoles are found in plats, animals, and single-celled organisms.
In plants, vacuoles can occupy up to 90% of the cell while in animals, vacuoles are much
smaller and also help store ions and nutrients.
Single-celled organisms that live in aquatic environments like the paramecium, have a
contractive vacuole to maintain homeostasis.
Based on the information given, how does a vacuole help an organism maintain homeostasis?
A. It helps by regulating water amounts within the cell.
B. It helps by keeping a rigid structure at all times,
C. It helps by excreting salt as part of osmosis
D. It helps by controlling the movement of gases into the cell.

Answers

Answer: c

Explanation: because it helps by excreting

What three air masses affect Pennsylvania’s weather the most, what are their air mass symbols and where do they come from

Answers

I think it might be, maritime polat(p), continental polar(p), and maritime tropical(mt). I hope this helped!

which of the following is least likely to be an example of a transference situation?

Answers

Transference is a psychoanalytic term that refers to the phenomenon in which an individual's feelings and emotions are unconsciously transferred from one person to another.

Transference occurs when people project onto others the emotions and attitudes that they once held towards significant figures in their past lives such as their parents, teachers, and early caregivers.

The following is the least likely example of a transference situation: An individual who dislikes his therapist for the first few sessions due to the therapist's personal habits (such as tapping his pen on the desk) but eventually comes to realize that the source of the negative emotions was the individual's own unresolved feelings about his father who used to make a similar noise.

The other options are more likely examples of a transference situation: An individual becomes romantically interested in his therapist, projecting onto the therapist the love and affection he once felt for his mother. A client who is unconsciously angry with her father is hostile towards her therapist, transferring her anger to the therapist, whom she unconsciously associates with her father.

An individual who feels insecure and inferior in social situations responds to his therapist with fear and trepidation, projecting onto the therapist the feelings he had towards his early caregivers.

For Further information on Transference visit:

https://brainly.com/question/28273708

#SPJ11

Which of the following is LEAST likely to be an example of a transference situation?

a. Clients who make you into something you are not

b. Clients who want information about the helping process

c. Clients who displace anger onto you

d. Clients who are not able to accept boundaries

help????? please and thank you​

Answers

Red I believe is the answer

who is the current preme minister of America​

Answers

Mr. Joe Biden

Mr. Joe Biden is the current president of the USA.

Joe Biden my bro hope it helps

Will give brainliest! Need help fast please....
Margo is interested in pursuing a degree in agriculture. To decide on a career field, what should she consider first?


desired working conditions and lifestyle

history of agriculture and benefits

types of livestock and crop production

innovations in farming and necessary education

Answers

Answer:

I would say desired working conditions and lifestyle, since everything you do would revolve around that. I'm not sure if it's correct though.

Explanation:

Answer:

C.

Explanation:



How does sexual reproduction increase genetic variation in a species?

a. All of these answer selections lead to an increase in genetic variation.

b. By producing gametes with different combinations of parental chromosomes.

c. By allowing recombining of chromosomes from two different individuals.

d. By allowing recombination of alleles on a chromosome.

Answers

The correct option is (d). Sexual reproduction is a process that increases genetic diversity in a species. It produces offspring with unique combinations of traits and genetic makeup.

Sexual reproduction is a process that increases genetic diversity in a species. It produces offspring with unique combinations of traits and genetic makeup. Sexual reproduction contributes to genetic variation in several ways, including producing gametes with different combinations of parental chromosomes, allowing recombination of chromosomes from two different individuals, and enabling the recombination of alleles on a chromosome. Sexual reproduction is one of the key factors in the generation of genetic variation in a population. Sexual reproduction is a process in which two individuals produce offspring that have unique combinations of genetic traits from both parents. The offspring produced are not identical to their parents or any other individual in the population. This variation arises because each gamete carries different alleles of the same gene. During fertilization, the gametes fuse, and the chromosomes of the two parents combine to produce a new individual. The new individual carries a unique combination of alleles, some of which may have come from one parent, and others that may have come from the other parent.The first way that sexual reproduction increases genetic variation is by producing gametes with different combinations of parental chromosomes. In humans, for example, each egg or sperm cell contains 23 chromosomes. When fertilization occurs, the egg and sperm combine to form a zygote, which now contains 46 chromosomes. The chromosomes in the zygote are a combination of the chromosomes from the mother and the father, which means that the zygote carries a unique set of genes that are different from any other individual in the population. A second way that sexual reproduction increases genetic variation is by allowing the recombining of chromosomes from two different individuals.

During meiosis, the cells that produce gametes undergo a process called crossing over. In this process, the chromosomes in the cell exchange segments of DNA with their homologous chromosomes. This creates new combinations of genes on the chromosomes, which are then passed on to the offspring. The result is that each gamete carries a unique combination of alleles, which contributes to genetic variation in the population. Finally, sexual reproduction increases genetic variation by enabling the recombination of alleles on a chromosome. An allele is a different version of a gene. Each individual carries two alleles for each gene, one inherited from each parent. During fertilization, the alleles on the chromosomes combine to produce a unique combination of genes in the offspring. This can lead to different traits in the offspring that are not present in either parent. Overall, sexual reproduction contributes to genetic diversity in a population by producing unique combinations of genes in the offspring. This allows the population to adapt to new environmental conditions, increasing the survival of the species in the long run.

To know more about Sexual reproduction visit: https://brainly.com/question/29541212

#SPJ11

Which of the following is the greatest source of salt in the Earth's ocean water?
Α.
chemicals eroded from the Earth's crust
В.
water falling from the Earth's atmosphere
C.
ice from the Earth's glaciers
D.
carbon dioxide released by the Earth's sea animals

Answers

Answer:

A. chemicals eroded from earth's crust

Which of the following is a form of ethnic segregation that persists in the
United States?
A. Immigrants are required to live together until they have become
naturalized citizens.
B. A federal law requires ethnic groups to live together until they
learn to speak English.
OC. Many American Indians still live on reservations where their tribes
had been relocated by force.
O D. Strong leaders encourage their followers to live together so that
they can control them more easily.

Answers

Answer:

C. Many American Indians still live on reservations where their tribes had been relocated by force.

Explanation:

Given that ethnic segregation has to do with the artificial separation of various people of different socio-cultural backgrounds.

Hence, the ethnic segregation that persists in the United States can be attributed to "Many American Indians still live on reservations where their tribes had been relocated by force."

Answer:

C. Many American Indians still live on reservations where their tribes

had been relocated by force.

Explanation:

In humans, the ability to taste the bitter chemical PTC is controlled by a single gene. The tasting gene (T) is dominant to the non-tasting gene (t).
Which of the following genotypes is correctly labeled?
Choose 1 answer:
A
tT - heterozygous recessive
B
Tt - hom0zygous recessive
C
TT - hom0zygous dominant
D
tt - heterozygous dominant

Answers

Answer: TT - hom0zygous dominant

Hope this helped! :)

Answer:

CORRECT (SELECTED)

TT - homozygous dominant

Explanation: Individuals with two tasting alleles are homozygous dominant.

Experiments have shown that adult human hearing is most sensitive in the frequency range of the sound of a human baby crying. Based on the threshold of audibility curve shown for an adult male shown below, into which frequency range does most babies' crying fall? Threshold of audibility equal-loudness curve A. 25 – 50 Hz B. 250 – 500 Hz C. 2500 – 5000 Hz D. 10,000 – 20,000 Hz

Answers

Answer:

The correct answer is - C. 2500 - 5000 Hz

Explanation:

According to the graph, there is the threshold of audibility curve that exhibits that at 2500 Hz and 5000 Hz, the lowest thresholds of audibility are present. So the sound that is faintest can be heard at 2500 Hz and 5000 Hz.

This is the reason that te humans are sensitive to the crying of the babies as they must cry at 2500 Hz and 5000 Hz frequency and we get their attention easily.

There are a number of similarities between microarray and mRNAseg methods. However, which of the following statements is not true of mRNAseq? The method requires cDNA synthesis. The method reports on the transcriptome. The method identifies which exons of a gene are expressed. The method requires a complementary probe. The method measures the relative number of each transcript in the sample

Answers

The mRNAseg and microarray approaches share several characteristics. It is not true with mRNAseq, however, that the approach analyses the relative number of each transcript in the sample statements. Hence (e) is the correct option.

The same set of samples were used to compare data sets from the RNA-Seq and Affymetrix platforms, and the results revealed a strong association between genes. A microarray is a laboratory technique used to simultaneously measure the expression of thousands of genes. A known DNA sequence or gene is contained in each of the thousands of small dots that are printed on microscope slides in certain locations. These slides are called DNA microarrays.

To know more about microarray, click here:

https://brainly.com/question/32224336

#SPJ4

There are a number of similarities between microarray and mRNAseg methods. However, which of the following statements is not true of mRNAseq?

a. The method requires cDNA synthesis.

b. The method reports on the transcriptome.

c. The method identifies which exons of a gene are expressed.

d. The method requires a complementary probe.

e. The method measures the relative number of each transcript in the sample

PLEASE HELP ME IM ON MY LAST ATTEMPT!!!!! I WILL MARK BRAINLEIST

Answers

Answer:

this goes from question on top as One

Explanation:

Top is "introduction of an antibiotic"

bottom is " a population resistant to antibiotic"

the second one is "a toxic agent"

the third is "bacteria"

fourth is "most of bacteria died"

Hi! Could You Help Me? - Pick A Scenario That You Believe Will Have The Greatest Impact On A Food Web In Your Local Ecosystem And Explain -

Answers

3: Trees are very eco friendly and they are what help us breathe natural air. They have a impact in a pro and con way. Pro, they build more stores, homes, and things we need in those spaces. Con: They are killing our fresh air and we don’t need that. The world is already going through disasters, and we are getting animals extinct.

In horses, the allele for long legs (L) is dominant over the allele for short legs (1). What is the
probability of short legs in the offspring of parents that are both heterozygous for the trait?

Answers

Answer:

[tex]\frac{1}{4}[/tex] or 25%

Explanation:

Heterozygous means that the organism has different alleles (L1)

Draw a punnet square:

       L           1

L     LL         L1

1      L1          11

11 is the allele for short legs so 1 in 4 of the outcomes will lead to an offspring with short legs

What is an autotroph? How does it obtain food? ​

Answers

Most autotrophs use a process called photosynthesis to make their food. In photosynthesis, autotrophs use energy from the sun to convert water from the soil and carbon dioxide from the air into a nutrient called glucose.

Answer:

answer below

Explanation:

An autotroph produces it own food. For example, Plants take sunlight and Water, and make their own food :)

In a one paragraph response, what findings in your iHuman assessment led you to select these two providers?

Answers

Based on the iHuman assessment findings, the two providers for further evaluation and consideration are demonstrated extensive knowledge and displayed exceptional skills.

Firstly, Provider A demonstrated extensive knowledge in the field of gastroenterology and exhibited a thorough understanding of chronic gastritis, its pathophysiology, and management strategies.

Secondly, Provider B displayed exceptional skills in mental health assessment and intervention. Their understanding approach, active listening, and appropriate response to the client's expression of hopelessness and potential ideation were notable.

Learn more about iHuman, here:

https://brainly.com/question/29902888

#SPJ4

Your question is incomplete, most probably the full question is this:

In a one paragraph response, what findings in your iHuman assessment led you to select these two providers? ihuman lin case ms washington neuroassessment

A tall plant of unknown genotype is test crossed. Of the offspring 869 are dwarf and 912 are tall. What is the genotype of the unknown parent?

Answers

The tall plant of an unknown genotype is test crossed . In the offspring, 869 are dwarf and 912 are tall. This indicates that the unknown parent's genotype was heterozygous because when an unknown parent is crossed with a homozygous recessive parent,

a 1:1 phenotypic ratio is expected. However, the ratio in this case is greater than 1:1 which shows that the genotype of the unknown parent was heterozygous i.e. Tt. It is important to note that if the unknown parent was homozygous dominant, then the offspring would have all been tall, while if the unknown parent was homozygous recessive, the offspring would have all been dwarf. Hence, the answer is "the genotype of the unknown parent was heterozygous (Tt)."More than 100 refers to the total number of offspring which is 869+912= 1781.

To know more about crossed visit:

https://brainly.com/question/12037474

#SPJ11


At which positions will result in the lowest high tides and the highest low
tides of the lunar month (smallest tidal range)?

О 1 and 5
0 1 and 3
O3 and 7
O4 and 8

Answers

I believe C is the answer

which of the following is a slow process that changes earth's surface?

flooding
volcanic eruption
earthquake
wind erosion​

Answers

Answer:

earthquake (i think)

Explanation:

I am pretty sure it is earthquake since it is slow to move the plates of the earth and it is slow for the earthquake to happen.

Seismographs rely heavily on a pendulum (free-swinging weight) to record measurements. How do you think using a pendulum helps detect small earthquakes?

Answers

Answer:

Generally, a seismograph consists of a mass attached to a fixed base. During an earthquake, the base moves and the mass does not. The motion of the base with respect to the mass is commonly transformed into an electrical voltage. The electrical voltage is recorded on paper, magnetic tape, or another recording medium.

Principle of a pendulum: a heavy, inert mass with a certain resistance to movement (i.e. inertia) due to its weight is suspended from a frame by a spring that allows movement. The energy from any seismic activity excites this “proof mass” as it is called by geophysicists, making it vibrate. When they detect movement, such as the shifting plates of an earthquake, a pendulum with a pen attached to it graphs the magnitude of the movement. If the pendulum swings vigorously, scientists know that the seismic waves are intense and potentially dangerous. My guess is, when pendulum swings lightly it determines mild intensity and small impact of an earthquake.

How would the author of "Are 'Green' Cars Really All That Green?" dispute the claim in "Cars Without Gasoline Are Here" that biofuels are a good replacement for fossil fuels? ​

Answers

Answer:

A. By noting that biofuels come from vegetables such as corn and sugar beet.

Explanation:

The author claims that biofuels are a good replacement for fossil fuels in the vehicles because it produced less carbondioxide gas as compared to fossil fuels. The biofuels also produced pollution but less as compared to fossil fuel. This biofuel is extracted in the form of Bioethanol which is a type of alcohol made by fermentation process of starch crops such as corn, sugarcane, or sweet sorghum. This biofuel made from biological materials that decrease the production of carbondioxide gas.

Other Questions
giving brainliest!!!!!!The _______ Trail made it possible for large groups to move west. The trail was _______ and _________. Find the area of the figure. What does it mean to be responsible? You wait for other people to tell you to do something. You try to get your friends to do your homework for you. You depend on your government to make the laws. You do what you are supposed to do. Sumita buys a set of earphones for 12.17.She pays with 15.How much change does she get?Give your answer in . American Sign Languageby Maria Baraza1 You've probably seen it before. Someone is giving a speech, and another person stands near the speaker, mouthing the speaker's words for people who can read lips. In a graceful dance, his or her arms and hands visually repeat the speaker's words in signs. If the speech is broadcast on television, the signer is sometimes shown in a window at the corner of the screen. Audience members who are hard of hearing or deaf can understand the speech through the signs.2 Deaf or hard-of-hearing people could also read the text of the speech, but it might not be available in writing. Besides, signing offers many advantages that reading cannot. Seeing the speaker, even if his or her words cannot be heard, can be important. The audience can observe the speaker's facial expressions and body language, which can change the meaning of the spoken words. The signer will often attempt to convey the speaker's tone or precise meaning with facial expressions that accompany the signs. For instance, when the speaker asks a question instead of making a statement, signers will raise their eyebrows, widen their eyes, and tilt their bodies forward to convey that what they are signing is a question.image3 Many different sign languages are used around the world. In the United States, most people use a system called American Sign Language (ASL). ASL is a complex, complete language, just like spoken English. ASL even has different "pronunciations" for certain words in different regions of the country. In ASL, some signs represent specific words. Touching one's fingers to the brim of an imaginary cap means "man." The sign was created when most men wore hats and would tip their hats when greeting someone.image4 However, most of ASL is based more on ideas than on words. For example, a person might hold both thumbs and index fingers at right angles and move both hands and arms apart. The person is indicating "big" or "large." The same sign would be used for a big man, a large amount of money, or a serious problem. When a person strokes an imaginary beard by moving a loose fist down from the chin, he or she is indicating "old." That same sign could describe an elderly person, an old car, or a story from long ago.image5 Many people believe in "total communication," which means saying words and signing them at the same time. A person might have only partial hearing loss, so he or she could hear some of the sounds the speaker makes. The speaker's lip movements, voice, signs, and facial expressions are like pieces of a puzzle. The theory is that total communication provides every possible means to get an idea across.6 Not every word or idea in English has a sign. Proper names and other words that have no signs are often spelled out with the sign alphabet. Sometimes the letters of the sign alphabet are used as words. For example, the sign for T and the sign for V together mean "television." Just like "TV" spoken aloud, the two sign letters indicate the word. In other cases, the full name of a person or thing is spelled out because there is no simple way to communicate it. If a person's name is Tina, she could use the signs for T-I-N-A.7 If you are not hard of hearing, why would you bother to learn sign language? For one thing, it will allow you to communicate with people who are hard of hearing or deaf. You can translate for them, helping them to understand others and be understood. Many people choose to make ASL translation their career. On an individual level, learning ASL will also help in forming friendships with deaf or hard-of-hearing people.8 Sign language can be useful for other reasons, even among hearing people. You might be too far away to hear someone, but not too far away to see the person. A couple of gestures can send an important message. Suppose you are in a situation in which you couldn't speak out loud, like in a theater. You might want to send a message to a friend who is not right next to you. It would be rude to shout while the performance is going on, but you could always send a sign message. Sign language can benefit people who are deaf, partially deaf, or hearing.Which of these sentences could be added to paragraph 7 to better conclude the paragraph? A. Translating for the deaf and hard of hearing can be a rewarding experience. B. There is growing demand for translators in business and education. C. American Sign Language will also let you communicate with people who can hear. D. American Sign Language can help you connect with people you may have been unable to before. Glycerin at 20'C flows upward in a vertical 75 mm diameter pipe with a centerline velocity of 1.0 m/s. Determine the pressure drop and head loss in a 10 meter length of pipe. Help me with this pls Write a linear (y= mx + b), quadratic ( y= ax^2), or exponential (y=a(b)^x) function that models the data. please look at the image and answer sections 8 (1,2,3,4) 9 (1,2,3) wanna know if my answer is correct (C.) please help!!!!Which of the following is the solution to the equation 2/3x = 12? A. X= 4 B. X= 8 C. X = 18 D. X = 24 A database is an efficient way to share information because it:A. is often the most significant source of error in an experimentB. provides the most precise measurement of a natural object.C. can be searched quickly for the most relevant observations.D. can evaluate the validity of a logical argument in a discussion. Write a rule for the nth term of the geometric sequence:a3=54, a6=1458 ECONOMICS QUESTIONHow can you describe examples of pure competition even though there are no pure competitive markets? Is it ethical for politicians to be able to invest in the stockmarket, given the way they have access to insider information?? Develop a strategic business plan for a POULTRY CHICKEN FARMING to be submitted to a lending institution so that you can borrow funds to start your small business. You are required to write an Company Description of a POULTRY CHICKEN FARMING in Australia. Your mortgage has 25 years left, and has an APR of 6.167% (with semiannual compounding) with monthly payments of $1,500.a. What is the outstanding balance?b. Suppose you cannot make the mortgage payment and you are in danger of losing your house to foreclosure. The bank has offered to renegotiate your loan. The bank expects to get $167,000 for the house if it forecloses. They will lower your payment as long as they will receive at least this amount (in present value terms). If current 25-year mortgage interest rates have dropped to 4.009% (APR with semiannual compounding), what is the lowest monthly payment you could make for the remaining life of your loan that would be attractive to the bank? John had 8 marbles and 4 red marbles in the bag. He took 1 marble from the bag and then replaced it and then took a second marble. What is the probability that john gets a red marble and then a red marble again? A: 1/9B: 3/4C: 1/3D: 1/11 Jlvesh is analyzing the flight of a few of his model rockets with various equations. In each equation, h isthe height of the rocket in centimeters, and the rocket was fired from the ground at timet = 0, where t ismeasured in seconds.Jivesh also has a more powerful Model B rocket. For this rocket, he uses the equation h=-90t4 + 300t.When is the height of the Model B rocket 250 centimeters? Round your answers to the nearesthundredth.After t =seconds, the rocket will have reached a height of 250 centimeters. One house key weighs 1/2ounce.Which model represents the total weight in ounces of 5 house keys? _____ percent of older people living in their own homes have lived there 20 years or longer.