2013高考英语经典陷阱题大串讲·it 用法
1. Everyone knows that _________ is dangerous to play with fire, but _________ is difficult is to prevent children from pl aying with fire.
A. it, it B. what, what C. it, what D. what, it
【陷阱】很容易误选B，认为两空均考查形式主语。
【分析】最佳答案是D，第一空填形式主语，真正的主语是其后的不定式 to play with fire。第二空填 what，what is difficult 是主语从句，注意 what is difficult 后的谓语动词 is。请做以下类似试题：
(1) I know _________ is important to know my own limitations, but _________ is difficult is to help others to know their own limitations.
A. it, it B. what, what C. it, what D. what, it
(2) Yes, _________ is difficult to find a job nowadays, but _ ________ is more difficult is try to find such a job with a high salary but little things to do.
