2017中考英語難點語法詳解:as與which的用法區(qū)別

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引導非限制性定語從句時,有時兩者可互換。如:
    I live a long way from work, as you know. 我住得離工作單位很遠,這你是知道的。
    1. 通常要用as的場合
    ①當從句位于主句前面時,只用 as。如:
    As is known to everybody, the moon travels round the earth once every month. 月球每月繞地球轉一周,這是每個人都清楚的。
    ②用于such, as, the same后引導限制性定語從句時,只能用as。如:
    I never heard such stories as he tells. 我從未聽過他講那樣的故事。
    This is the photo which shows my house. 這張照片拍的是我的住宅。
    2. 兩者的細微區(qū)別
    ①as引導的非限制性定語從句應與主句在意義上和諧一致,which無此限制。如:
    He went abroad, as was expected. 他出國了,這是大家預料到的。
    He went abroad, which was unexpected. 他出國了,這讓大家感到很意外。(不用as)
    ②as引導非限制性定語從句時,先行詞通常不能是主句中某個具體的詞,而應是整個句子、整個短語或某個短語推斷出來的概念,而which 則無此限制。如:
    The river, which flows through London, is called the Thames. 這條流經(jīng)倫敦的河叫泰晤士河。(不用as)
    ③當as引導非限制性定語從句作主語時,其謂語通常應是連系動詞,而不宜是其他動詞,而 which則無此限制。如:
    She has married again, as seemed natural. 她又結婚了,這似乎很自常。
    She has married again, which delighted us. 她又結婚了,這使我們很高興。(不用as)