句型13.
It +谓语＋段时间＋before+主语＋谓语.（ before引导的是时间状语从句。） 如：
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。
句型14.
It is +形容词(possible, impossible, necessary等) ＋for+ sb.+ to do. 如：
It is impossible for me to finish this work before tomorrow.我明天之前完成此工作是不可能的。
句型15.
It is +（心理品质方面的）形容词＋of + sb. +to do.= 主语+ be +形容词＋to do.(常用的形容词有：kind, stupid; foolish, good, wise等。)如：
It is kind of you to help me.＝You are kind to help me.你真好给我提供了帮助。
句型16.
由as引导的非限定性的定语从句。如：
As we have known, he is a most good student.众所周知，他是个很好的学生。请比较：It is well-known that he is a most good student.（前一个是定语从句，而后者是个主语从句。）作者: xiaomeixin 时间: 2010-12-21 10:50
Thank you very much.
It's important for us to learn this sentence well.
