We must know what we should do and what we should avoid a good impression on others in public places.
A. to leave
B. leaving
C. to have left
D. leave
网友回答
(答案→)A. to leave
B. leaving
C. to have left
D. leave
解析：句意：在公共场合，为了给其他人留一个好的印象，我们必须知道我们该做什么，我们应该避免做什么。表示目的“为了……”，故用不定式，选A。