1.If you (finish) reading this book,please return it to me.
答案:have finished
2.If you (know) how I suffered,you would pity me.
答案:knew
3.If you had been there then,you (stop) him doing that.
答案:would have stopped
4.If you had studied at high school,you (be) a student of a key university now.
答案:would be
5.Without your timely help,we (not complete) that task on time.
答案:couldn’t/wouldn’t have completed
