1. 宾语从句:有whatwhich hat引导句子在整个句子充当宾语成分，就是宾语从句。eg:i don't know what to do.i don't know which one is the best.我不知道该做什么。我不知道哪一个是最好的。2. 状语从句:以时间，原因，等引导词在整个句子中充当状语成分的就是状语从句。eg:i don't know she is my english teacher when i see her at first time.我第一眼见到她的时候，不知道她是我的英语老师。