题目内容
（请给出正确答案）
[单选题]
orbit [5C:bit] （）
A.n． 脚踏车, 自行车
B.n． 周期, 循环, 自行车, 一段时间, 整套, 周波 vi． 循环, 轮转, 骑自行车 vt． 使循环, 使轮转
C.n． 轨道, 势力范围, 生活常规, 眼眶 vt． 绕…轨道而行 vi． 进入轨道, 沿轨道飞行, 盘旋
D.n． 球, 球状物, 子弹, 舞会, 尽情地玩
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will be living in space within the next hundred or so
years. Planet Earth will be crowded, dirty and lack of 【S1】______
resources. A sort of exodus (移居) of mankind will
begin.
Spaceships will be assembled so that they revolve
around the earth. Some may orbit around Mars. These
space stations will be serviced by space buses. We saw
the first space bus launch in April 1981. This was 【S2】______
"Columbia", it made several orbits around the earth and 【S3】______
then returned, landing on a huge dry lake bed in
California. "Columbia" will be used again. Previous
spaceships have been abandoned, only the nose cone
being used to bring the crews back to earth. 【S4】______
Upon established, each space station will generate 【S5】______
its own atmosphere and have its own agriculture. It will
need to rotation to provide an artificial gravity; people 【S6】______
will be forced inwards from the centre by centrifugal 【S7】______
(离心力) force.
The moon and Mars could become new sources of
new materials. Driving through space will no longer 【S8】______
need Earth fuel—the energy would come from the
sun. This energy would be converted from electricity to 【S9】______
work magnetic rockets.
That all sounds quite fantastically but, with the 【S10】______
rapid development of modern technology, who knows
about what the future holds?
【S1】
