这个and是多余的
请看下面的题：
When the last prize had been awarded _____ everybody cleared off.
A. and B. so
C. or D. 不填
【陷阱】容易想当然地误选A。
【分析】句首 when 引导的是一个时间状语从句，它暗示整个句子为复合句；而so, and, or 为并列连词，无论选哪一个，都表明整个句子为并列句，从而导致前后矛盾，所以A、B、C均不能选择。此题正确答案选D，everybody cleared off 为整个复合句的主句。请看类似例子(from www网址未加载)：
(1) If wishes were horses, _____ beggars would ride.
A. and B. so
C. or D. 不填
(2) If I’m mistaken, _____ you are mistaken too.
A. so B. and
C. or D. 不填
(3) Just before I left London, _____ I sent him a telegram.
A. and B. so
C. or D. 不填
(4) After they had each said a few words, _____ Lloyd George took the floor.
A. and B. so
C. or D. 不填
答案均选D，空格前分别为 if, when, before, after 引导的状语从句，空格后为整个复合句的主句。
