19.9 比較until和till
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   此兩個連詞意義相同。肯定形式表示的意思是"做某事直至某時",動詞必須是延續(xù)性的。否定形式表達的意思是"直至某時才做某事"。動詞為延續(xù)性或非延續(xù)性都可 以。 正確使用這兩個連詞的關(guān)鍵之一就在于判斷句中的動詞該用肯定式還是否定式。
 
  肯定句:
  I slept until midnight. 我一直睡到半夜時醒了。
  Wait till I call you.  等著我叫你。
  (在肯定句中可用before代替 Let's get in the wheat before the sun sets.)
 
  否定句:
  She didn't arrive until 6 o'clock.
  她直到6點才到。
  Don't get off the bus until it has stopped.
  公共汽車停穩(wěn)后再下車。
  I didn't manage to do it until you had explained how.  直到你教我后,我才會做。

1)Until可用于句首,而till通常不用于句首。
   Until you told me, I had heard nothing of what happened.
   直到你告訴我以前,出了什么事我一點也不知道!
2)Until when 疑問句中,until要放在句首。
  ---Until when are you staying? 你呆到什么時候?
  --- Until next Monday. 呆到下周一。 

注意:否定句可用另外兩種句式表示。
(1)Not until …在句首,主句用倒裝。
   Not until the early years of the 19th century did man know what heat is.
   直到19 世紀初,人類才知道熱能是什么。
   Not until I began to work did I realize how much time I had wasted.
  直到我開始工作,我才認識到了我已蹉跎了幾多歲月。
(2) It is not until… that…















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