1. It is + adj. (for sb.) + to do sth.“对某人来说做某事是怎样的。”
常用形容词：dangerous (危险的), difficult (困难的), easy (容易的), hard (艰难的), important (重要的), impossible (不可能的), interesting (有趣的), necessary(必要的), pleasant(舒适的), safe(安全的), useful(有益/用的)等
It is difficult to see and hear at the back.
It is important for Liu Sanzi to work on his father’s farm.
学生认真听老师讲课是非常必要的。______________________________________________
▲提示：避免句子头重脚轻，其中It做形式主语，不定式才是真正主语，翻译时先译不定式。
2. It is + adj. + (of sb.) to do sth. “某人做某事是怎样的。”
It’s very kind of you to help me.
It’s foolish of him to go alone.
▲提示：这一句型中常用描述行为者的性格、品质的形容词。如careful(细心的), careless(粗心的),clever(聪明的), foolish(愚蠢的), good(好的), kind(友善的), lazy(懒惰的), nice(友好的), polite(有礼貌的),right(正确的), wrong(错误的)等。
3.形容词+不定式
a.表示感情或情绪的形容词后面常接不定式，这样的形容词有：glad(高兴的), pleased(高兴的), sad(忧伤的), thankful(感激的)等, 如：
I’m glad to see you. I’m very sad to hear the bad news.
b.表示能力和意志的形容词，如able(有能力的), certain(一定), ready(乐意的，有准备的),sure(一定)等常接不定式。如：
He is able to swim.
Lily is alw
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