special difficulties

非限制性定语从句的代词：

（1）who引导的非限制性定语从句，主要指人做主语

e.g.

主句是：Mr. Smith was a famous person in American history.

非限制性定语从句：Mr. Smith, who died on July 17th at 84, was a famous person in American history.

e.g.

非限制性定语从句：There were very few passengers, who escaped without serious injury.游客很少，他们都逃出来了，没有受重伤。

限制性定语从句： There were very few passengers who escaped without serious injury. 没有受重伤而逃出来的游客很少。

（2）指代事物在非限制性定语从句当中只能使用which，不能用that（但是在限制性定语从句中，可以用that）

e.g. He lent me a thousand dollars, which was exactly the sum I needed. 他借了我一千美元，这正是我所需要的。

（3）指代时间用when, 指代地点用where

e.g. He was left on the desert island, where he stayed for as long as three weeks. 他被滞留在荒岛上，在那里他呆了长达三周之久。

whenever, whoever, whatever wherever, whichever , however 加强句子的语气 ＝no matter when / who / what / where / which / how

e.g. You can telephone me whenever you like.

e.g. Whichever day you come, we'll be pleased to see you.

e.g. Whenever you go, I'll follow you.新概念英语3

e.g. However busy you are, you must spare some time to study English.

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