单选题
Which of the following statements is not characteristic of liquid-fuel rockets?
A、
The fuel is cheap.
B、
They are cheap to build.
C、
They can be stopped and re-ignited.
D、
They must be used soon after fueling.
【正确答案】
B
【答案解析】
文中指出a liquid-fuel rocket is an expensive device，选项B说其造价低，与文意不符。
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