as which引导定语从句哪个不缺成分

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.
as, which 用在句末的时候,有些情况下可以互换使用.
He was late for school,as/which was usual with him．他上学迟到,这是家常便饭.
He was a foreigner,as/which I knew from his accent．他是个外国人,我从他的口音中得知这一点.
I live a long way from work,as/which you know．我离上班的地方很远,你是知道这一点的.
The author was brought up in a small village, as/which is recounted in some of his stories. 作者是在一个小村庄里长大的,这个问题在他的一些小说了就被提到过.
但是,当主句是否定句时,只能as.例如：
Spiders are not insects, as many people think. 蜘蛛不是昆虫,而许多人却认为蜘蛛是昆虫.
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.

.as,which引导的定语从句,修饰整个句子
1）as引导的定语从句可以放在句首,句中,句末,从句中的动词常常是know,understand,see,report,---带有一种众所周知的意思
The earth is round,as is known to us all.地球是圆的,这一点大家都知道.= As is known to us all,the earth is round.= The earth,as is known to us all,is round.
2）which引导的这样的定语从句只能放在从句后,动词没有限制.
He didn`t pass the English exam,which made his parents disappioted.他没有通过英语考试,这使他的父母很失望.