1. It's +形容词+ of+ sb. +动词不定式
这一句型表示"某人(做某事)……"。常用形容词有：good, kind, nice, polite, clever, foolish, lazy, careful, careless, right, wrong等，来说明"人"的性质或特征。
It's very kind of you to help me. 你能帮助我真是太好了。
It's foolish of you to make such mistake. 你真傻啊，竟然犯这种错误。
2. It's +形容词+for + sb. +动词不定式
这一句型表示"做某事对某人来说……"。常用形容词有：difficult, easy, hard, dangerous, safe, useful, pleasant, interesting, impossible等，来说明动词不定式的性质、特征。
It is impossible for a child to answer the question. 小孩子不可能回答出这个问题。
It's dangerous for you to swim alone. 你自己一个人去游泳很危险。
3. 主语+be动词 +形容词+动词不定式
这一句型常用表示感情或情绪的形容词，如：glad, pleased, sorry, sad, thankful等以及表示能力和意志的形容词，如:ready, able, sure, certain等。
I'm very sorry to hear the news. 听到这个消息我很难过。
I'm glad to see you. 见到你我很高兴。
Comrade Lei Feng is always ready to help others. 雷锋同志总是乐于帮助别人。
Tom is sure/ certain to come. 汤姆一定会来。
