What is the most important factor for a rocket to escape from the Earth? How fast will a rocket go to escape completely from th

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问题 What is the most important factor for a rocket to escape from the Earth?
How fast will a rocket go to escape completely from the Earth’s gravity? ______

选项 A、Seventy miles per second.
B、Seven thousand miles per hour.
C、Twenty-five thousand miles per second.
D、Twenty-five thousand miles per hour.

答案D

解析 从文章的第二段最后一句,可以得知逃离地心引力的速度是每秒7英里或者每小时2万5千英里。所以本题的答案应该是D。
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