问题
选择题
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
答案
答案:B
这题考查独立主格结构,结构是:名词+非谓语,此句前后句没连词,只有逗号是不能连接两个句子的,所以后边the most recent ______ at the end of last March就是独立主格的形式了,在句中做伴随状语,又因为事情发生在过去,所以用现在分词完成时。选B。