is clear to us all students should obey the school’s rules.A. AsB. WhatC. WhichD. It

问题补充：

is clear to us all, students should obey the school’s rules.

A. As

B. What

C. Which

D. It

答案：

(答案→)A. As

B. What

C. Which

D. It

解析：在非限制性定语从句中，As代替后面出现的整个概念。