题目内容
The country has already sent up three unmanned spacecraft, the most recent __________ at the end of last March.
A. has been launched B. having been launched
C. being launched D. to be launched
C。
解析:
由于动作于去年的三月底就已经发生,所以不能选表示未来动作的不定式,即不能选D; 又由于句子用了具体的过去时间状语(at the end of last March),故不能选完成式,即不能选A和B。

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