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
B
解析:the most recent having been launched构成独立主格结构。the most recent指最近发射的载人飞船,与launch是被动关系所以要用动词+ing形式的完成式的被动式。
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