is known to everybody the moon travels round the earthonce every month.A. It 　　　　B. As 　

问题补充：

is known to everybody, the moon travels round the earthonce every month.

A. It

B. As

C. That

D. What

答案：

A. It

(答案→)B. As

C. That

D. What

解析：本题考查定语从句。本题考查由as引导的非限定性定语从句，as作“正如”之意。句意：正如大家所知道的，月亮每个月绕地球一次。