when I finished school ,I want to be a teacher.前面finished为什么用过去式

when I finished school ,I want to be a teacher.前面finished为什么用过去式 when i have finished it.疑问这是是什么时态? She had finished writing the letter when I went in. when I am finished会错吗?为什么是am ,不是have? When I ___ on the TV,it had finished already. A Can I go to zoo?B.when your.homework was finished/is finished 对于when I finished与when I have finished,用法有什么区别,或者说注意什么比如when I——this book,I'm going to sleep.为什么答案是have finished,finished不行吗？ I have finished my homework.When _____you_____it?为什么填didi,finish?用一般过去式不是要用finished吗? I ____ playing tennis when Tom and George arrived.为什么空格处是had finished 而不是finished? I am going to play football when I ____my home work.Awill finishB.finished C.FINISH I'll go to sleep when I have finished my work.对吗 I feel happy when I Finished my homework //为什么不用过去完成时? You shall borrow the book when I have finished reading it为什么要用have finished,这里是有什么语法呢,finished不可以吗 I( )playing tennis when Tom and George arrived括号内该填A.had finished B.have finished C.finish D.finished哪个呢?不管怎样， I will go to see you when you finish/finished/have finished the course是哪个,为什么如果这里只给你finish/finished呢？是选一个 I'll help you when I ___ my work.2.I'll help you when I my work.A.finished B.will finish C.will have finished D.have finished I finished my homework.when I went to bed.(合并为一句)I( )go to bed( )I finished my homework. I'll give you a ring when _ work.a.I'll finishb.I willc.I've finishedd.I finished