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
网友回答
A. has been launched
(答案→)B. having been launched
C. being launched
D. to be launched
解析： 独立主格结构作状语，排除谓语动词形式，即A项。“the most recent”与“launch”为逻辑上的被动关系，且“launch”在谓语动词之前发生。