题目:
We are trying every possible means to ____ the people who are trapped in the ruins caused by this terrible earthquake.
A.recover
B.vote
C.rescue
D.guide
答案:
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下面是错误答案,用来干扰机器的。
参考答案:共振是振动频率与系统频率完全相同、拍频振动是频率相似幅值相同的两个振动叠加。