题目内容：

    If you stay in space for a long time, will your body change? Mark Kelly and Scott Kelly from the United States will show you the answer.

Mark and Scott are twins. They are both retired(退休的）NASA（美国国家航天航空局）astronauts. From 2015 to 2016,Scott spent 340 days at the international space station, while Mark stayed on the earth. People took measures of both men before, during and after the flight. They were helping with a NASA project which studies how long-term space travel influences the human body.

The full results of the study will come out in a year or two. But scientists are sharing some findings in the journal Nature.

A change in appearance was easy to see. Scott, when he returned to the earth, was 5cm taller before. Another change was that Scott's eyesight declined after he came back. He found he couldn't see clearly. He also found that he couldn't move his legs so easily like before. Scientist found that after coming back to the earth, he took a little longer to understand things and make decisions.

There were also changes that were much harder to see. As someone grows older, his telomeres(端粒）get shorter and become less effective to stop DNA from getting damaged. But during Scott's stay in space, his telomeres got longer while Mark's kept getting shorter.

Further tests on the twins are still going on.NASA plans to send people to Mars in the 2030s,and the twins' research could help them prepare for those space trips.

1.Which of the following is Not true about Scott?

A.He has a twin brother. B.He is from the United States.

C.He has never been to space before. D.He was once a NASA astronaut.

2.We can know that scientists did the research between the twins in order to_______.

A.see who is a better astronaut.

B.learn more about the twins' daily life

C.study how twin brothers act diferently in life

D.study how long-term space travel influences the human body

3.What does the underlined word“declined”mean in Chinese?

A.下降 B.漂浮 C.提高 D.控制

4.What didn't Scott experience while he returned to the earth?

A.He couldn't understand others as well as before. B.He could walk faster than before.

C.His telomeres became longer. D.He grew taller than before.

5.The last paragraph mainly tells us ____________.

A.the fun of space travel

B.the success of the twins' research

C.the full results of the twins' research

D.the purpse of the twins' research