7. Carbon nanotubes could be used to make the skins of spacecraft because____.
A. they are much lighter than metal
B. they are 600 times stronger than steel
C. they can shield the spacecraft from radiation
D. they can break ions in space rays
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8.What will happen when ions hit the metal on a spaceship?
A. Some worse radiation will be produced.
B. All radiation will be blocked out.
C. The metal on the spaceship will break up.
D. The ions will move at high speeds.
9.Tiny sensors will be built into the new spaceship so that______.
A. the computer brain can feel the smallest pinpricks
B. the spaceship can have human sensations
C. the sensors can send signals to the spaceship
D. the spaceship will be capable of repairing itself
10. What is the passage mainly about?
A. How to build a future spaceship.
B. How to make use of carbon nanotubes.
C. How to protect astronauts in space.
D. How to block out radiation.
在一个C++源程序中,main函数的位置( )。
A. 必须在程序的最开始
B. 可以任意
C. 必须在程序的最后
D. 必须在其它函数之前
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