it 用作形式主语可以代替哪些成分

it 用作形式主语可以代替哪些成分

it用作形式主语时可代替不定式、动名词、从句等。一般说来，当不定式、动名词、从句等复杂成分用作句子主语时，为保持句子平衡，通常把真正的主语放在句末，而在句首使用形式主语it。

1. 代替不定式

It is difficult to make crossing over a sea. 横渡大海是件难事。

It is very easy to deal with Australians. 与澳大利亚人打交道容易。

It is dangerous to bathe in the sea here. 在这儿的海里游泳是危险的。

It is her custom to go for a walk on Saturday morning. 她惯常在星期六早上出去散步。

It is difficult to breathe at these altitudes. 在这些高的地方人们会感到呼吸困难。

It is pleasant to walk among the trees in the evening. 晚上在树林中走一走令人心旷神怡。

It is advisable always to wear a safety belt when you’re driving. 开车的时候最好总是系着安全带。

2. 代替动名词

It is nice visiting new places. 到陌生地方去玩真是有意思。

It is man’s social being that determines his thinking. 人的社会存在决定人的思想。

It is a bore having to go out again on a cold night like this. 像今天这样的夜晚还得出门真烦死人。

3. 代替从句

It is appropriate that he (should) be present. 他应到场才对。

It is astonishing to me that he should be absent. 他竟未出席令我惊讶。

It is well known that Edison invented the electric bulb. 众所周知，是爱迪生发明了灯泡。

It is desired that this rule should be brought to the attention of the staff. 希望这条规则引起全体职员的注意。

It is a question that needs very careful consideration. 这是一个需要仔细考虑的问题。(G31)

It was astonishing to everybody that the court had made such a decision. 法庭作出这样的判决，所有人都感到很惊讶。

It is amazing that she should have said nothing about the murder. 令人惊奇的是她对这桩凶杀案竟然不置一词。