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

问题补充：

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

A. was launched

B. being launched

C. has been launched

D. having been launched

答案：

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。