1.This is the house in which we lived last year.这里的in which可用where替代
This is the house (which/that) we visited last year.
2.Can you tell me the reason why he is unhappy?
Is this the reason which you give to me
3.I have ten apples, all of which are sweet.虽然前面有个all,但这里不能用that替换which ,
4.The girl (which/that)I met yesterday is my neighbor.
5.Do you still remember the days which we spent many years ago together?