20.2 比较and和or
 
 1) 并列结构中,or通常用于否定句,and用于肯定句。

 2) 但有时and 也可用于否定句。请注意其不同特点:
   There is no air or water in the moon.
   There is no air and no water on the moon.
 在否定中并列结构用or 连接,但含有两个否定词的句子实际被看作是肯定结构,因此要用and。

典型例题
 ---I don't like chicken ___ fish. 
 ---I don't like chicken, ___ I like fish very much.
 A. and; and  B. and; but C. or; but D. or;and
 答案C。否定句中表并列用or, but 表转折。

判断改错:
  (错) We will die without air and water.
  (错) We can't live without air or water.
  (对) We will die without air or water.
  (对) We can't live without air and water.
 





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