定语从句中，只能用，which，且不用that：
1、引导非限制性定语从句时，当关系词前有介词时。
2、在一个句子中有两个定语从句，其中一个定语从句的关系代词用了that, 另一个应用which。
3、当关系代词后面有插入语时。
4、先行词为that时。
拓展资料
which
1. He lived on an invalidity pension which came as a weekly giro.
他靠每周领取的作为病残养老金的直接转账救济支票过日子。
2. Politicians want a lap-dog press which will uncritically report their propaganda.
政客们想要的是不问是非、甘为他们搞宣传的哈巴狗一样的新闻媒体。
3. We were in the same college, which was male-only at that time.
我们那时在同一所学院，当时只招男生。
4. We gained a rich supply of data which would normally be inaccessible.
我们得到了通常难以获取的大量数据。
5. "Which one of these do you want?" — "I don't mind."
“你想要这里面的哪一个？”——“都可以。”
6. A formal contract is signed which is renewable annually.
正式签订了每年可续签的合同。
7. He was already asleep in the bed, which smelled faintly of mildew.
他已经在略带霉味的床上睡着了。
8. Show me which one you like and I'll buy it for you.
指给我看你喜欢哪个，我给你买。
9. Why not retrain for a job which will make you happier?
为什么不接受新的培训，找一份让你更快乐的工作？
that
1. A miracle is something that seems impossible but happens anyway.
奇迹就是看似不可能，却发生了。
2. If you wait, all that happens is that you get older.
如果你等待，发生的只有变老。
3. When life gets hard and you want to give up, remember that life is full of ups and downs, and without the downs, the ups would mean nothing.
当生活很艰难，你想要放弃的时候，请记住，生活充满了起起落落，如果没有低谷，那站在高处也失去了意义。
4. Eventually, you'll learn to cry that on the inside.
终有一天，你会学会让泪往心里流。
5. Success is not final, failure is not fatal: it is the courage to continue that counts.--Winston Churchill
成功不是终点，失败也并非末日，最重要的是继续前进的勇气。
6. It's not about making the amazing saves. It's the little things and small things that made great gatekeepers great.
伟大的门将不是靠神奇的扑救成就，而是靠注重小事和细节成功。（Tim Howard美国国家队门将）
7. The turning point in the process of growing up is when you discover the core of strength within you that survives all hurt.
当你从内心深处找到一种可以忍受一切痛苦的坚强力量时，你的成长历程就会出现飞跃。
限制性定语从句:限制性定语从句与先行词之间的关系比较密切，对所修饰的先行词起修饰限制作用，如果去掉，会影响句子的主要意思的完整。
非限制性定语从句:非限制性定语从句与主句之间的关系不太密切，它只是对所修饰的先行词或句子进行补充说明，如果去掉从句，也不会影响句子的主要意思，主句的意思依然完整。
所以which当然肯定引导非限制性定语从句