as/which引导定语从句的区别

　　(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引导定语从句时，其先行词为整个主句。which引导非限制性定语从句，其先行词也可以是主句或主句中的一部分。

　　(3)与主动动作先后不同：as从句表示的行为经常是在主句行为之前，而which引导的定语从句表示的却在主句之后，表示连续发生的事情或结果等。

　　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.

　　注意先行词为时间、地点或原因时，关系词的选用

　　如果用when, where 或why，关系词在从句中应该是做状语,否则的话则应该用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

　　用作状语的从句叫状语从句(adverbial clause).