问题
选择题
_______ in the regulations that you should not tell other people the password of your e-mail account.
A．What is required
B．What requires
C．It is required
D．It requires
答案
答案：C
句子中的it是形式主语，代替后面由that引导的主语从句。require的宾语从句中要用虚拟语气，It is required 后接的主语从句中也要用虚拟语气，即should加动词原形。