题目内容：

“I bought this shirt for 35 Yuan yesterday.” “It’s on sale today for only 29.You should have waited.” “Oh,really?But how ______ I know?
A.would B.can C.did D.do

优质解答

C 是过去式.使用过去式的时候,那个action必须发生在过去并且已经结束：＂How did I know?＂=＂我怎么知道的?＂说明那个Subject已经知道了.A是条件式.条件是通常是一种懊悔／感叹,意思就是没有发生,因为一些条件不具...