It is well known to us all China sent up a manned spaceship to outer space successfully l

问题补充：

It is well known to us all China sent up a manned spaceship to outer space successfully last year.

A. that

B. what

C. which

D. when

答案：

A. that

B. what

C. which

D. when

解析：句中it作形式主语,真正的主语是由that 引导的从句。