What is the most important factor for a rocket to escape from the Earth? Why is it not necessary to provide powered flight in s

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问题 What is the most important factor for a rocket to escape from the Earth?
Why is it not necessary to provide powered flight in space all the time?

选项 A、Few spacecrafts complete their flight operations.
B、The Earth’s gravity cannot be overcome.
C、No future power is needed after the escape speed is reached.
D、Free fall takes the place of the Earth’s gravity pull.

答案C

解析
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