问题补充：
We worked all night, for the coming procession.
A. to prepare
B. preparing
C. prepared
D. was preparing
答案：
A. to prepare
(答案→)B. preparing
C. prepared
D. was preparing
解析：作状语的现在分词短语常用逗号与句子的其它部分隔开,而作目的状语用的动词不定式短语只有置于句首时,才可以用逗号隔开.当然,若去掉逗号,答案则变成A.
