in the regulations that you should not tell other people the password.
A. What is required
B. What requires
C. It is required
D. It requires
网友回答
A. What is required
B. What requires
(答案→)C. It is required
D. It requires
解析：考查it形式主语。本题的it是形式主语，真正主语是that you should not tell other people the password.