when he opened his bag on the train,he found that he------to put the clean shoes inA forgot B forget C had forgot D would forget选那个那,我选C但是自己说不清楚为什么
问题描述：
when he opened his bag on the train,he found that he------to put the clean shoes in
A forgot B forget C had forgot D would forget选那个那,我选C但是自己说不清楚为什么
答
C had forgot
动作发生在found 之前， 所以用过去的过去，过去完成时。
答
语感可以解释么。。。
不过从语义上也可以，表示的是发生的事情，有“已经”的意思
答
C
从上下文看,因为前面是过去时（打开包）,这里就应该用过去完成时（忘记带干净鞋子在打开包之前就已经发生了）