when, while與as

And there are times when reading electronically is simply impractical, for example when standing in a very crowded train.

(a)when (b)as

這是一題克漏字測驗,平常我學的英文文法是[When+簡單式], [While+進行式], [As+進行或簡單式]

但這題為什麼是when+V-ing

又底線部分為什麼不能用"as"代替呢?

請問 when, while及as 的相關文法內容 謝謝!

1 Answer

Rating
  • Louis
    Lv 7
    1 decade ago
    Favorite Answer

    when可以當conjunction, question adverb, relative adverb用

    while可以當conjunction, noun用

    as可以當adverb, conjuntion, preposition用

    And there are times when reading electronicall is simply impractical, for example when standing in a very crowded train.

    本句的times是名詞,意思是時間,後面有一個形容詞子句(即關係子句)來限定它,

    但形容詞子句己經有了自己的主詞了,子句的意思和times的關係是時間,所以子句本身需要一個代表時間的關係副詞,來和主句相連,所以只有when這個字具備此條件.

    2010-02-03 19:33:37 補充:

    子句的主詞是動名詞片語reading electronically,我少打了一個字母y

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