不定式主語
1） It's easy (for me) to do that.我做這事太容易了easy, difficult, hard, important, possible, impossible, comfortable, necessary, better;
the first, the next, the last, the best, too much, too little, not enough
It's so nice to hear your voice.
聽到你的聲音真高興。
It's necessary for you to lock the car when you do not use it.
當你不用車的時候，鎖車是有必要的。
2) It's very kind of you to help us. 他幫助我們，他真好。
Kind, nice, stupid, rude, clever, foolish, thoughtful, thoughtless, brave, considerate(考慮周到的), silly, selfish(自私的)
例句:
It was silly of us to believe him. 我們真愚蠢，竟然相信了他。
It seemed selfish of him not to give them anything. 他不給他們任何東西，這顯得太自私了。
注意：1) 其他系動詞如，look，appear等也可用于此句型
2) 不定式作為句子成分時，動詞用單數形式。
3) 當不定式作主語的句子中又有一個不定式作表語時，不能用It is… to…的句型
(對)To see is to believe. 百聞不如一見。
(錯)It is to believe to see.
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