替代作主语的从句、动词不定式、动名词,而把真正作主语的从句、动词不定式、动名词
置于句尾。
It 作形式主语的常见句型:
1. 代作主语的动词不定式,其句型为
(1) It be adj. (for sb.) to do sth.
此处adj. 通常为描述事件的形容词:easy, difficult, hard, necessary, unnecessary,
possible, impossible, likely, unlikely, right, wrong, important, unimportant, legal,
illegal, well-mannered, ill-mannered, polite, impolite, clear, obvious, certain,
suitable, proper, fit, useful, useless, dangerous…
例 It is illegal (for a teenager) to drive a car without a license.
(2) It be adj. of sb. to do sth.
此处adj. 通常为描述人的形容词:kind, unkind, nice, rude, cruel, considerate,
thoughtful, thoughtless, careful, careless, silly, foolish, stupid, clever, wise, crazy.
例 It's kind of you to help me with the problem.
(3) It 替代作主语的动名词的常见句型
It's no good/use doing…
It's (well)worth doing…
It's (well)worth one's while doing/to do…
It's (well)worth while doing/ to do
例 It's no use crying over spilt milk.
2. It 替代作主语的从句常见句型
(1) It is + noun +从句
例 It is no secret that the president wants to have a second term at office.
(2) It is adj. +clause
It's surprising that… (should)………竟然……
It's a pity/shame that…(should)………竟然……
例 It's important that you should apologize to her for your rudeness.(=It's of
much importance that you should apologize to her for your rudeness.)
(3) It verb sb. + clause= It is v-ing + clause
It+surprise/delight/interest/disappoint/worry/disturb/annoy/amaze
/bother/concern/frighten/please/anger sb. that…
例 It worried me that she drove so fast.(= It was worrying that she drove so
fast.)
(4) It verb (to sb.) that…= sb/sth verb to do
(verb = appear, seem, come about, emerge, follow, chance, happen, occur,
transpire, turn out , work out)
例 It (so) happened/chanced that they were out.(= They happened/chanced
to be out.)
(5) It is v-ed that…=sb/sth is to do
(verb=say, report, think, believe, hope, expect, agree, accept, decide,
determine, intend, plan, understand, know)
例 It is said that the couple have gotten divorced.(=The couple are said to