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A.a single type of multipotent stem cell found in the bone marrow
B.differentiated cells that first developed in the fetal liver, but now reside in the bone marrow
C.division of differentiated cell types while circulating in the blood
D.stem cells that became committed to each specific blood celll type during embryonic development
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更多“The many different cell types in the blood of an adult mammal are derived from().”相关的问题
第1题
阅读理解 Passage 1 Manners evolved differently in different cultures. In earlier times there was a tendency for manners to become increasingly formal, and this was often viewed as progress. In the 18th and 19th centuries having good manners was seen as an important part of one’s education and social class, and it was necessary to be taken as a lady or a gentleman to get ahead in the world. In the 20th and 21st centuries, manners have gradually become more relaxed and informal. The hosting of dinners and other social gatherings are no longer the exclusive privilege of the wealthy elite (精英), and private clubs are being gradually replaced by more open meeting places. So the manners of the salon (沙龙) are gradually combining with the manners of the pub. Clothing is a good indication of the changes in manners, as can be seen in the following examples. It is surprising that the wearing of hats indoors by males is once again becoming acceptable. Students in North America often wear baseball caps to class. In many countries the wearing of hats indoors by males was once acceptable even in very polite society, but over the years this became considered as a lower-class behavior. and was thus discouraged in both the middle and upper classes. The young people who wear hats indoors do not realize they are actually restarting a very old cultural tradition. A comparable development for females is the wearing of jeans. Many females now wear jeans on a daily basis, either at home or at work. Some see this as a symbolic declaration that they are now modern women, not girls or ladies. Some girls, like boys, wear baseball caps both indoors and outdoors. Sneakers and shorts are now acceptable for either males or females in a variety of non-athletic situations. Some companies have rules requiring informal dress such as jeans or sneakers on Fridays (called “dress-down Friday” or “casual Friday”), and others permit it almost all the time. In these companies, and many others, it is acceptable to call the bosses by their first names. 1 What does the passage mainly talk about？
A、Changes of manners over time.
B、Formal manners in the earlier times.
C、Different manners in different cultures.
D、Development of manners in different classes.
第2题
School buildings themselves can show liberal (开明的) or conservative views about what should go on in a classroom. The earliest schools had separate classrooms for different grades. The rooms were laid out formally, with pupils’desks fastened to the floor in straight rows facing the teacher’s desk. Clearly, such schools reflected a teacher-and-subject-centered view of education. Schools of the next generation had more open space, and most had movable desks. They also often provided special rooms or areas for science, art, music, and physical education. There were still separate rooms for different grade levels, however, and the desks still were likely to be formally arranged. That is, the schoolroom was still largely designed to carry out the old-school program, which involved grade levels, uniform. time blocks, and study of subject matters. Newer subjects, not newer teaching methods, accounted for most of what was new in school design. The first school buildings constructed to encourage liberal teaching methods appeared in the mid-1950s. Folding interior (内部的) walls permitted the flexible use of space to encourage large-group, small-group, or individual instruction. Some provided carrels for individual study, areas for team teaching, and centers for programmed instruction. In the newest buildings called open schools, the use of space is even more flexible. Areas within the buildings can be readily expanded for program changes, and used for many kinds of functions. One should remember, though, the physical layout (布局) of a school cannot decide whether it has the conservative or liberal teaching practices. What determines whether the classroom is liberal or conservative is the spirit and attitude of the teacher. The word “carrel” in Paragraph 3 most probably refers to ________.
A、a room with folding walls
B、a room with liberal instructions
C、a room with conservative instructions
D、a room with small space
第3题
A visitor to India should remember it is impolite there to use the left hand for passing food at the table.The left hand is for washing yourself.Also in India, you might see a man shaking his head at another to show that he is disagree ing.But in many parts of India a side-to-side movement of the head is to show agreement.In Bulgaria you shake your head to show "yes"—a nod shows "no".
In Europe it is quite usual to cross your legs while sitting and talking to someone, even at an impor tant meeting.But doing this could cause offence to a Thailander.Touching the head of a grown-up is also not done in Thailand.
Knowing about manners is useful when you are traveling, and you also need to know the language used to express the customs.
1.If you are staying in India, you'd better().
A.not use your left hand to pass food at the table
B.use your left hand to pass food at the table
C.not use your left hand to wash yourself
D.use your left hand at all times
2.To shake your h ead means “Yes” ().
A.in India
B.in Europe
C.in Bulgaria
D.in Thailand
3.You can easily make a Thailander angry by().
A.touching his head
B.crossing your legs while talking to him
C.shaking your head
D.nodding your head
4.The wri ter thinks that to know about a country well one must().
A.know the language of the country
B.know the manners of the country
C.know the manners better than the language
D.know both the language and the manners
5.We can learn from the passag e that().
A.different countries have different manners
B.the manners in Thailand are the same as those in India
C.one should be careful not to cross legs in Europe
D.one should not touch a grown-up's head in India
第4题
Losing your ability to think and remember is prettyscary. We know the risk of dementia (痴呆症) increases with age. But if you have memory slips, you probably needn't worry. There are pretty clear differences between signs of dementia andage-related memory loss. After age 50, it's quite common to have trouble remembering the names of people, places andthings quickly, says Dr. Kirk Daffner of Brigham and Women's Hospital in Boston. The brain ages just like the rest of the body. Certain parts shrink, especially areas in the brainthat are important to learning, memory and planning. Changes in brain cells can affectcommunication between different regions of the brain. And blood flow can be reduced asblood vessels narrow. Forgetting the name of an actor in a favorite movie, for example, is nothing to worry about. Butif you forget the plot of the movie or don't remember even seeing it, that's far moreconcerning, Daffner says. When you forget entire experiences, he says, that's "a red flag that something more seriousmay be involved." Forgetting how to operate a familiar object like a microwave oven, orforgetting how to drive to the house of a friend you've visited many times before can also besigns of something going wrong. But even then, Daffner says, people shouldn't panic. There are many things that can causeconfusion and memory loss, including health problems like temporary stoppage of breathingduring sleep, high blood pressure, or depression, as well as medications (药物) likeantidepressants. You don't have to figure this out on your own. Daffner suggests going to your doctor to checkon medications, health problems and other issues that could be affecting memory. And the bestdefense against memory loss is to try to prevent it by building up your brain's cognitive (认知的) reserve, Daffner says. "Read books, go to movies, take on new hobbies or activities that force one to think in novelways," he says. In other words, keep your brain busy and working. And also get physicallyactive, because exercise is a known brain booster.Why does the author say that one needn't be concerned about memory slips？ 1..Why does the author say that one needn't be concerned about memory slips？()
A、Not all of them are symptoms of dementia.
B、They occur only among certain groups of people.
C、Not all of them are related to one's age.
D、They are quite common among fifty-year-olds.
第5题
Like the press in most other countries, American newspapers range from the “sensati onal”, which feature crime, sex and rumor, to the serious, which focus on factual news and the analysis of world events.But with few exceptions American newspapers try to entertain as well as give information, for they have to compete with television.
Just as American newspapers give way to all tastes, so do they also try and apply to readers for all political persuasions.A few newspapers support extremist (过激分子)groups on the far right and on the far left, but most daily newspapers attempt to attract middle-of-the-road Americans who are essentially moderate.Many of these papers print columns by well-known journalists of different political and social views in order to present a balanced picture.
As in other democratic countries American newspapers ca n be either responsible or irresponsible, but it is generally accepted that the American press serves its country well and that it has more than once bravely uncovered political scandals (丑闻)or crimes, for instance, the Watergate Affair.The newspapers dr ew the attention of the public to the fears of the Vietnam War.
1.There are fewer national newspapers in ().
A.Britain than in the U.S.A
B.France than in Britain
C.the U.S.A.than in Britain or France
D.France than in t he U.S.A.or Britain
2.Most American newspapers try to entertain their readers because ().
A.they have to keep up a good relation with them
B.they have to compete with television
C.they have to write about crime, sex and rumor
D.t hey have to give factual news in an interesting way
3.Many American newspapers attract readers of different political tendency by ().
A.supporting extremist groups from time to time
B.inviting middle-of-the-road Americans to write articles for them
C.avoiding carrying articles about extremists
D.printing articles representing different political viewpoints
4.In this passage the underlined word “press” (Para.2) means ().
A.a machine for printing
B.the business o f printing
C.great force
D.newspapers
5.The passage is mainly about ().
A.the characteristics of American newspapers
B.the development of American newspapers
C.the functions of American newspapers
D.the m erits and shortcomings of American newspapers
第6题
What are the beauties of Hawaii？ Let’s start with four.
The beach, famous for its water temperature, air temperature and waves, is the first beauty.There are hundreds of miles of beaches on the twenty islands of Hawaii.They are thought to be among the finest beaches in the world.
Then, what do you think would be the second beautiful thing？ It is volcanoes (火山), of course.These volcanoes are not just a part of the islands; they made the islands in the first place.Because of them the islands are still growing.
What would be the third thing of beauty that the first visitor to Hawaii would notice？ It probably wouldn’t be just one thing, but many things: all the wonderful fruits and flower s of the islands.Sugar cane, bananas and pineapples are Hawaii’s biggest exports.Sugar cane has been growing in Hawaii for a thousand years.As for pineapples, the islands produce more than any other places in the world, which has made Dole Company the b iggest fruit-packing company in the world.
The fourth and most beautiful thing about Hawaii is the people who live there.The Hawaiians never rush, and perhaps this is because they care more for human life than they care for the machine.There is an old H awaiian law that a man can go to sleep in the middle of the road if he wants to.What makes the people of Hawaii so beautiful is their feeling about people.There are 64 different combinations of races on the islands, and they all live in peace.They belie ve “Above all nations is humanity.” That is the most beautiful thing of all.
1.According to the passage, Hawaii is made up of().
A.one island
B.twenty islands
C.sixty-four islands
D.hundreds of islands
2.Why are the volcanoes so special to the islands？()
A.They are not a part of the islands
B.They actually made the islands
C.They are the first in the world
D.They are growing
3.What has made Dole Company the biggest fruit-packing company in the world？()
A.Sugar
B.Sugar cane
C.Bananas
D.Pineapples
4.The people in Hawaii are the most beautiful thing because().
A.they had a peaceful history
B.they can sleep in the middle of the road
C.there are 64 different races on the islands
D.they care more for people than anything else
5.According to the passage, “above all nations is humanity” might mean ().
A.not all nations have humanity
B.humanity is as important as a nation
C.humanity has no national boundaries
D.all human being s should live in peace
第7题
Meaningfulness affects memory at all levels.Information that does not make any sense to you is difficult to remember.There are several ways in which we can make material more meaningful.Many people, for instance, learn a rhyme to help them remember.Do you know the rhyme "Thirty days has September, April, June, and November..."？ It helps many people remember which months of the year have 30 day s.
Organization also makes a difference in our ability to remember.How useful would a library be if the books were kept in random order？ Material that is organized is better remembered than jumbled information.One example of organization is chunking.C hunking consists of grouping separate bits of information.For example, the number 4671363 is more easily remembered if it is chunked as 467, 13, 63.Categorizing is another means of organization.Suppose you are asked to remember the following list of wor ds: man, bench, dog, desk, woman, horse, child, cat, chair.Many people will group the words into similar categories and remember them as follows: man, woman, child; cat, dog, horse; bench, chair, desk.Needless to say, the second list can be remembered mo re easily than the first one.
Association refers to taking the material we want to remember and relating it to something we remember accurately.In memorizing a number, you might try to associate it with familiar numbers or events.For example, the heigh t of Mount Fuji in Japan -12,389 feet -might be remembered using the following associations: 12 is the number of months in the year, and 389 is the number of days in a year (365) added to the number of months twice (24).
The last principle is visualizati on.Research has shown striking improvements in many types of memory tasks when people are asked to visualize the items to be remembered.In one study, subjects in one group were asked to learn some words using imagery, while the second group used repetiti on to learn the words.Those using imagery remembered 80 to 90 percent of the words, compared with 30 to 40 percent of the words for those who memorized by repetition.Thus forming an integrated image with all the information placed in a single mental pict ure can help us to preserve a memory.
1.What kind of information is easy for us to remember？()
A.Information that does not make any sense to us
B.Information that we are not familiar with
C.Information that is meaningful to us
D.Information that we are not interested in
2.Which of the following pairs are rhymes？()
A.horse—house
B.right---white
C.come----home
D.how---low
3.The second list of words in para.3 is organized according to().
A.the rhyme
B.the word category
C.th e first letters of words
D.the meanings
4.Books are kept in a library().
A.according to their size
B.in random order
C.in a jumbled way
D.in different categories
5.What method can better help form. a whole mental picture about the ti ngs to be remembered？()
A.Grouping
B.Repetition
C.Imagery
D.Association
第11题
He returned from his first visit to the place in late autumn, and could not get back until the snow melted in the following spring.Then he went to the pilot of a small plane, who earned his living by carrying hunters over parts of the country where there were no roads and no railways.He asked the pilot to take him back to the piece of forest.
The pilot did not know the place, so the hunter showed it to him on the map.“But there is nowhere to land there,” said the pilot.“I have flown over that we can’t land anywhere between this river and these mountains.”
“I thought you were a wonderful pilot,” said the hunter, “some of my friends said you could land a plane on a postage stamp.”
“That’s right,” answered the pilot.“I can land a plane where nobody else can.But I tell you there is nowhere to land in the place you are talking about.”
“And what if I tell you that another pilot did land me there last spring？” said the hunter.
“Is that true？” asked the pilot.
“Yes, it is.I swear it.”
Well, this pilot could not let himself beaten by another, so he agreed to take the hunter.
When they reached the place, the hunter pointed out a small spot without trees in the middle of the forest, with a steep rise(陡坡) at one end.The pilot thought there was not enough room to land there, but the hunter said that the other pilot had done so the year before, so down went the plane.When it came to the rise, it turned right over onto its back.As the hunter climbed out, he smiled happily and said, “Yes, that is exactly how the other pilot managed it last time.”.
6.The hunter in the story went to the forest ().
A.once
B.two times
C.many times
D.none of the above
7.In the story the hunter asked a pilot to take him to the piece of forest.This pilot was ().
A.the same pilot who had taken him to the place once
B.a different pilot who had never been to that part of the country
C.a pilot who had been to the place many times
D.a pilot who had never heard of such a place
8.It was difficult for the pilot to land the plane because ().
A.the place for landing was as big as a room
B.the place for landing was as small as a postage stamp
C.there wasn't any place to land
D.there was a room near the landing place
9.“When it came to the rise, I turned right over onto its back.” What do the words “its back” refer to？()
A.the back of the rise
B.the pilot’s back
C.the back of the plane
D.the back of the small spot
10.The hunter got to the plane the first time().
A.by jumping out of the place during the flight
B.in an entirely different way
C.exactly the same way as he got there the second time
D.by climbing down the tree on which the place hand landed
