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.nmet168.com)：

(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。