至可以插在主句之中。which引导的非限制性从句只能放在主句之后。

　　As can be seen from his face, he is quite pleased.

　　＝He is quite pleased, as can be seen from his face.

　　从他的表情可以看出，他非常高兴。

　　Li Ming was late, which made Mr. Zhang very angry.

　　李明迟到了，这使张先生非常生气。

　　(2)which在从句中可作实义动词的主语，as不可。

　　He came late again, which made his teacher very annoyed.

　　他又迟到了，这让老师非常生气。

　　(3)当从句和主句语义一致时，用as或which，若主、从句语义不一致，用which。

　　She has married again, as/which was expected.

　　她又结了婚，这是预料中的事。(语义一致)

　　She has married again, which was unexpected.

　　她又结了婚，这是出乎意料的事。(语义不一致)

　　集中演练2

　　2－1.用as或which填空

　　①As we all know, he studies very hard.

　　②Taiwan, as is known to all, is an inseparable part of China.

　　③He was late for the meeting, which made the chairman very angry.

　　④I want to buy the house, which has a garden.

　　⑤The elephant is like a snake, which is not right.

　　2－2.完成句子

　　⑥众所周知，他是我们班上最好的学生。

　　As is known to all, he is the best student in our class.

　　⑦他历史没有考及格，这看来是很自然的。

　　He failed in the history examination, as/which seemed natural．

　　⑧汤姆取得了很大进步，这使我们很高兴。

　　Tom has made great progress, which delighted us．

　　⑨李明迟到了，这事是经常发生的。

　　Li Ming is late, as is often the case.

　　⑩戴维是个摄影师，你是知道的。

　　David, as you know, is a photographer.

　　4．限制性定语从句与非限制性定语从句的区别

(1)引导词不同：关系代词that，关系副词why均不可以引导非限制性定语从句。