We must know what we should do and what we should avoida _________ good impression on others in public place．

A.to leave

B.leaving

C.to have left

D.leave

答案及解析： A

解析：

句意：我们必须知道在公共场合应当做什么，应当避免什么以给别人留下一个好印象。空格处是目的状语，所以要用不定式。