is known to everybody, the noon travels around the earth once every month.
A. It
B. As
C. That
D. What
网友回答
A. It
(答案→)B. As
C. That
D. What
解析：本题考查as引导的非限制定语从句。as作“正如……”解时，引导的非限制性定语从句来修饰整个句子。当as在从句中作主语时，常用于下列短语：as is known、as is said、as is reported、as is announced等。要注意掌握作关系代词引导定语从句的用法。