爱华网1． _____ is known toall，China will be an_____ powerful country in 20
or 30years'time．
A．That；advancingB．This；advancedC．As；advanced D．It；advancing
2．He made anotherwonderful discovery， _____ of great importance to science．
A．which I think isB．which I think itisC．which I think itD．I thinkis
分析：第一题考查了 as在从句中作主语的定语从句，意为“正如”，而ad- vanced
country表示发达国家；第二题考查了which引导的非限制性定语从句，I think是插入语。这两个句子分别含有as和 which引导的定语从句，现就其用法作一说明：
一、as引导的定语从句表示说话人对话语的看法、态度、依据、解释或评论。具有下列特点：
1．as用于引导定语从句时，具有“正如……、像……、由……而知”等语义。如：
He was strongly against the plan，as could be expected．（正如所料，他强烈反对这项计划。）
As he hoped he would，hesaw the girl．（像他希望的那样，他见到了那个女孩。）
2．as引导的定语从句在语义上要和主句保持一致，而which可不一定，如果语义不一致，则要用which来替代as。如：
He married again，as（which）wasnatural．（他又结婚了，这是自然的。）
3．as引导的定语从句，其先行词可由以下词来修饰，the same ／such ／as等。也可以由
which来改写，但不可直接替换。如：
This is the same sum as was spent in that year on privatemotoring．＝This is
the sum which was spent in that year on privatemotoring．（这与那年用于私人汽车所花的费用相同。）
4．as引导的非限制性定语从句可放在主句之后，也可放在主句之前。但which只能放在主句之后。如：
As we have seen，oceanscover more than 70％ofthe earth．（如我们所见，海洋覆盖地球70％多的面积。）
He seemed a foreigner，which in fact he was．（他看上去像个外国人，事实上他就是。）
5．as在定语从句中作宾语时，从句的谓语动词常是see ／watch ／know ／hear等表示感知的动词，且谓语动词前带有情态动词can ／could ／may等，此外常用的动词还有say ／
tell ／remember等。如：
It was true，as everybodycould know．（这是真的，大家都知道。）
6．as在定语从句中作主语时，其谓语动词可以是及物动词的被动语态，也可以是be或其它连系动词。如是不及物动词，则不存在以上关系。可以说as often hap- pens（appears）等。如：
He came back yesterday，as was ex- pected．（他如期昨日返回。）
二、which引导的此类从句，是对主句所叙述的事情进行补充说明，表明事物的状态或结果。一般有下列特点：
1．如果定语从句的谓语是行为动词的主动语态，且关系代词在从句中作主语时，一般要用which，这时which可以用 andthat改写为并列句。如：
Things then greatly changed，which surprised us．＝Things then greatly changed，and that surprised us．（那时事情巨变，使我们惊讶。）
2．由“介词＋关系代词”引导的关系分句多用于正式文体中，常用“介词＋ which”，不用“介词＋as”。如：
They tried to think of a plan by which they could finish their taskahead of time．（他们试图想个计划，以便提前完成任务。）
三、在与上述几条不冲突的情况下，as和which可以换用。如：
A horse is a useful animal，as ／whicheverybody knows．（众所周知，马是有用的动物。）
练习：
1．Dorothy was alwaysspeaking highly of her role in the play，_____ ，of course，madethe others unhappy．（NMET2000）
A．whoB．whichC．thisD．that
2．The weather turned outto be very good， _____was more than we could expect．
A．whatB．whichC．thatD．it
3．In the office I neverseem to have time until after 5：30P．M．_____ manypeople have gothome．（上海 95）
A．whose timeB．thatC．on whichD．by which
4．_____，the Great Wall came into beingin Qin Dynasty．
A．It's clearB．We all knowC．As we all knowD．Which we allknow
5．As many members werepresent _____ agreed to the plan．
A．whoB．thatC．whichD．as
6．_____ is known toeverybody，the moon trav-els round the earth once every month．（NMET 2001）
A．ItB．AsC．ThatD．What
（参考答案：1．B2．B 3．D 4．C 5．D6．B）
