The Earth has a force that pulls things toward itself. We call this force gravity (地心引力). This is something we live with all th

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问题    The Earth has a force that pulls things toward itself.  We call this force gravity (地心引力). This is something we live with all the time, and we take it for granted and hardly ever think about it. But it is a most important factor in rocket operation and

选项 A、To travel as fast as it can.
B、To overcome the Earth gravity.
C、To get away from the air resistance.
D、To have strong power in its operation.

答案B

解析 从文章的第一段最后一句“地心引力是火箭飞行中的一个重要因素,如果我们想到达太空或者离开地球,我们就必须脱离地心引力”,可以得出本题的答案应为B。
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