18.6 as,which 非限定性定语从句 |
由as,which 引导的非限定性定语从句,as和which可代整个主句,相当于and this或and that。As一般放在句首,which在句中。 As we know,smoking is harmful to one's health. The sun heats the earth,which is very important to us. 典型例题 1)Alice received an invitation from her boss,___came as a surprise. a.it B.that C.which D.he 答案C.此为非限定性从句,不能用 that修饰,而用which.,it 和he 都使后句成为句子,两个独立的句子不能单以逗号连接。况且选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B。which可代替句子,用于非限定性定语从句,而what不可。That不能用于非限定性定语从句,it不为连词,使由逗号连接的两个句子并在一起在英语语法上行不通。 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在引导非限制性定语从句时,这两个关系代词都指主句所表达的整个意思,且在定语从句中都可以作主语和宾语。但不同之处主要有两点: (1)as引导的定语从句可置于句首,而which不可。 (2)as代表前面的整个主句并在从句中作主语时,从句中的谓语必须是系动词;若为行为动词,则从句中的关系代词只能用which.。 在本题中,prevent由于是行为动词,所以正确选项应为B。 As的用法 例1.the same… as;such…as 中的as 是一种固定结构,和……一样……。 I have got into the same trouble as he(has). 例2.as可引导非限制性从句,常带有'正如'。 As we know,smoking is harmful to one's health. As is know,smoking is harmful to one's health. As是关系代词。例1中的as作know的宾语;例2中,它充当从句的主语,谓语动词know要用被动式。 |