由as, which 引導的`非限定性定語從句,as和which可代整個主句,相當於and this或and 一般放在句首,which在句中。例如:
As we know, smoking is harmful to ones health. 如我們所知,吸菸有害健康。
The sun heats the earth, which is very important to us. 太陽使地球暖起來,這對我們人類很重要。
典型例題
1)Alice received an invitation from her boss, ___came as a surprise.
A. it B. that C. which D. he
答案C. 此為非限定性從句,不能用 that修飾,而用which.,it 和he 都使後句成為句子,兩個獨立的句子不能單以逗號連線。況且選he句意不通。
2)The weather turned out to be very good, ___ was more than we could expect.
A. what B. which C. that D. it
答案h可代替句子,用於非限定性定語從句,而what不可。That 不能用於非限定性定語從句,it不為連詞,使由逗號連線的兩個句子並在一起在英語語法上行不通。
3)It rained hard yesterday, ____ prevented me from going to the park
A. that B. which C. as D. it
答案B. as 和which在引導非限制性定語從句時,這兩個關係代詞都指主句所表達的整個意思,且在定語從句中都可以作主語和賓語。但不同之處主要有兩點: