When people lose legs after accidents or illnesses, emergency care and artificial limbs（假肢）often allow them to walk again. Newts （蠑螈） in the same situation, on the other hand, can grow limbs back on their own! Scientists have known for a long time that certain animals can re-grow limbs, but they haven’t quite figured out how these creatures do it.
Researchers have now come up with some new ideas. Their work may give people the ability to re-grow lost limbs. The researchers started with two simple experiments：when you cut a newt’s leg at the ankle, only the foot grows back；when you cut off a leg at the very end, the whole leg grows back. In both cases, the re-growth begins with stem cells. Stem cells can develop into nearly any type of cell in the body.
How do a newt’s stem cells know when to grow only a foot and when to re-grow a whole leg?
This question relates to another mystery. In newt’s, a cut-off leg will grow back only if the nerve bundle（神經(jīng)束）in it also grows back , but if something prevents the nerve bundle from growing, the stem cells at the wound won’t re-grow a new leg.
In its study, a British team focused on a protein called n-AG. When the team prevented nerves in a limb from growing, but added the n-AG protein to stem cells in the limb, the limb still re-grew. That protein seems to guide limb re-growth. People have proteins that are similar to n-AG. Further research into these materials may someday help human limbs recover by themselves.
40. In the experiments, the researchers cut off a newt’s foot or leg to find out _____.
A. what stem cells were                    B. whether they would grow back
C. how long it would take to re-grow    D. how they would re-grow
41. A newt will re-grow its leg if _____.
A. its ankle was cut off but the nerve bundle was good
B. its leg was cut off and the nerve bundle stopped growing
C. its leg was cut off and the nerve bundle could grow back
D. its ankle and the nerve bundle were cut off
42. What do the underlined words “these materials” refer to?
A. Nerve bundles and proteins.         B. Proteins similar to n-AG.
C. Stem cells and proteins.              D. Stem cells and nerve bundles.
43. The first sentence of the passage _____.
A. acts as a lead–in                      B. shows where researchers got their new ideas
C. states the author’s opinion           D. describes the result of researchers’ studies

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  C. find out the reason why the Africans’ skin colour is dark

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科目：高中英語 來源： 題型：閱讀理解

Can people change their skin colour without suffering like pop king Michael Jackson? Perhaps yes. Scientists have found the gene that determines skin colour.

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Scientists have changed the colour of a dark-striped zebrafish to uniform gold by inserting a version of the pigment(色素) gene into a young fish. As with humans, zebrafish skin colour is determined by pigment cells, which contain melanosomes(黑色素). The number, size and darkness of melanosomes per pigment cell determines skin colour.

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Can people change their skin colour without suffering like pop king Michael Jackson? Perhaps yes. Scientists have found the gene that determines skin colour.

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  C. they have fewer activities outside

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Can people change their skin colour without suffering like pop king Michael Jackson? Perhaps yes. Scientists have found the gene that determines skin colour.

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However, Keith Cheng, leader of the research team, points out that the mutation is dif ferent in human and zebrafish genes.

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  B. the new discovery could lead to search into ways to change skin colour safely

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  D. find out the ways of changing peopl’s skin colour

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閱讀理解
     That cold January night, I was growing sick of my life in San Francisco. There I was walking home 
at one in the morning after a tiring practice at the theater. With opening night only a week away, I was 
still learning my lines. I was having trouble dealing with my part-time job at the bank and my acting at 
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too much for me. As I walked down empty streets under tall buildings, I felt very small and cold. I began 
running, both to keep warm and to keep away from any possible robbers. Very few people were still 
out except a few sad-looking homeless peopl e under blankets.
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see someone with a knife or a gun. The street was empty. All I saw was a shining streetlight. Still, the 
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in his eyes. "Is this what you're looking for?" he asked, holding up a small square shape.
     It was nearly 3 a.m. by the time I got into bed. I wouldn't get much sleep that night, but I had got my 
wallet back. I also had got back some enjoyment of city life. I realized that the city couldn't be a bad 
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B. Lucky and hopeful
C. Satisfied and cheerful              
D. Disappointed and helpless
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B. getting used to the city life
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B. talked a lot with a garbage truck driver
C. was robbed of her wallet by a man with a knife  
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B. would stay on in San Francisco
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