is known to everybody the moon travels round the earth once every month.A. ItB. AsC. Tha

问题补充：

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

A. It

B. As

C. That

D. What

答案：

A. It

(答案→)B. As

C. That

D. What

解析：考察从句连词选择。根据句子结构可知，该句为非限制性定语从句，从句中缺少is的主语，代指后面的 the moon travels round the earth once every month