The country has already sent up 3 unmanned spacecraft, the most recent at the end of last

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A. was launched
B. being launched
C. has been launched
(答案→)D. having been launched
解析：考查独立主格结构：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，the most recent和launch是被动关系，而且是去年三月已经被发射了，用现在分词完成式的被动式。句意：中国已经发射了3颗无人飞船，最近在去年的三月已经被发射。选D。