5.4 助動詞have的用法
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1)have +過去分詞,構(gòu)成完成時(shí)態(tài),例如:
   He has left for London. 他已去了倫敦。
   By the end of last month, they had finished half of their work. 
   上月未為止,他們已經(jīng)完成工作的一半。

2)have + been +現(xiàn)在分詞,構(gòu)成完成進(jìn)行時(shí),例如:
  I have been studying English for ten years.
  我一直在學(xué)英語,已達(dá)十年之久。

3)have+been +過去分詞,構(gòu)成完成式被動語態(tài),例如:
  English has been taught in China for many years.
  中國教英語已經(jīng)多年。







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