4. as引导非限定性定语从句并在从句中作主语时，其后面的谓语动词大多数必须是连系动词。如果从句谓语动词是行为动词，则必须用which。

He married her, as was natural.

She refused to take the medicine, which made her mother angry.

It rained hard yesterday, which prevented her from going to Shenyang.

He is absent, as is often the case.　　　　　　　　　　　　　　　　 The end

Choose the best answers:

3.as引导非限定性定语从句时，意为“这一点、这件事”，常与 see， hope，expect，know，guess等动词搭配；而which引导非限定性定语从句时与主句有一种因果关系，可译为“所以……”。

Cyprus, as you all know, is in the Mediterranean.

Bamboo is hollow, which makes it very light.

2.which 引导的非限定性定语从句一般放在句未，而as 引导的非限定性定语从句

可放在句未，也可放在句中、句首。 放在句首时不能用which 替换。

Crusoe lost his dog, which made him very sad

Taiwan is part of China, as/which is known to all.

As we have seen, oceans cover more than 70 percent of the earth.

1.　　 非限定性定语从句位于句未，而且as 和which 在从句中作主语、宾语、表语时

可互换。

He is a farmer, as/which is clear from his manner.

This elephant is like a snake, as/which anybody can see.

7.　　 as 做主语,表语,宾语; 先行词可以是一个词,一个短语或一个句子.

To shut your eyes to facts, as many of you do, is foolish.

As we all know, he studies very hard.

As 引导的定语从句可放在主句前,也可放在主句后.在很多情况下已经

构成固定搭配.

As everybody can see　　　　　　 as was usual

As can be seen　　　　　　　　　 as I expected

As is known to all，　　　　　　　 as may be imagined

as you know　　　　　　　　　　 as is expected

as has been said before　　　　　　 as is reported

as is often said　　　　 　　　　　　as is announced

限定性定语从句和非限定性定语从句的区别：

限定性定语从句是先行词在意义上不可缺少的定语，如果去掉，主句的意思就不完整或失去意义。这种从句和主句的关系十分密切，写时不用逗号分开。

非限定性定语从句和主句的关系不十分密切，只是对先行词作些附加的说明，如果去掉，主句的意思依然清楚。这种从句和主句之间往往用逗号分开，一般不用that 引导。

*　　　 *　　　　 *　　　　　 *　　　　　 *　　　　　　　 *　　 　　　*　

as和 which 引导的非限定性定语从句的比较：

6.　　 when 指时间,作状语.

The meeting will be put off till next month, when we will have made all the preparations.

5.　　 where 指地点, 作状语.

Galileo lived in the city of Pisa, where there is a leaning tower about 180 feet high.

4.　　 which 指物, 做主语,宾语.

His speech, which bored everyone, went on and on.

The speech, which he had written on the paper, seemed endless.

3.　　 whose 指人, 作定语.

The Chairman’s daughter, whose name is Ann, gave Tom a smile.

2.　　 whom 指人, 作宾语.

He had many friends, many of whom had been in the universities.