as/which引導定語從句的區別

　　(1)位置不同：as可置于句首，也可置于句中，而which只能放在句中。

　　(2)指代不同。 as引導定語從句時，其先行詞為整個主句。which引導非限制性定語從句，其先行詞也可以是主句或主句中的一部分。

　　(3)與主動動作先后不同：as從句表示的行為經常是在主句行為之前，而which引導的定語從句表示的卻在主句之后，表示連續發生的事情或結果等。

　　As was expected, the England team won the football match.

　　He promised to help me, which he did.

　　He was often late for work, which cost him his job.

　　注意先行詞為時間、地點或原因時，關系詞的選用

　　如果用when, where 或why，關系詞在從句中應該是做狀語,否則的話則應該用which / that等。例如：

　　I will never forget the days ________ I spent with my friends in the country.

　　that/which/ \

　　exercises

　　1. The boy was paid $10 for washing ten windows, most of ____ hadn’t been cleaned for at least a year. (2005/10)

　　A.those B.these

　　C.that D.Which

　　2. Anyone ______ has something interesting to concentrate on won't find life boring. (2005/4)

　　A. whoever B. whomever

　　C. who D. which

　　D C

　　3. Athletes ______ at the Olympic Games are supposed to be nonprofessionals. (2004/10)

　　A. who compete B. who are competing

　　C. who will compete D. who have competed

　　4. Television, ______ came into being in 1939, did not become common until the early 1950s. (2004/4)

　　A. that B. what

　　C. which D. it

　　A C

　　Adverbial Clauses

　　用作狀語的從句叫狀語從句(adverbial clause).