问题
选择题
_____ in the library regulations that any book borrowed be returned by due time, or the borrower will be fined．
A．What is required
B．It is required
C．As is required
D．Which is required
答案
答案：B
考查从句关系词的选择。根据句子结构可知该句为主语从句，it 作形式主语。
="=what" is required in the regulations is that …………
="As" is required in the regulations, …………