11. It is well-known that+从句。 众所周知
It is well-known that she is a learned(知识渊博) woman.
12. It is +段时间+since+主语+did. / It was +段时间+since+主语+had done.
It is five years since he left here.他已经离开这儿五年了。
It was five years since he had left here.(同上)
注意: It is five years since he lived here.他从这儿搬走已经有五年了。
13. It +谓语+段时间+before+主语+谓语.( before引导的是时间状语从句。)
It wasn't long before the people in that country rose up.
没有多久那个国家的人民就起义了。
It will be three hours before he comes back..三个小时之后他才能回来。
14. It is +形容词(possible, impossible, necessary等) +for+ sb.+ to do.
It is impossible for me to finish this work before tomorrow.
15. It is +(心理品质方面的)形容词+of + sb. +to do.
= 主语+ be + adj. +to do. (常用的有kind, stupid; foolish, good, wise等。)
It is kind of you to help me. =You are kind to help me.
