1、Could you make sure---------- ? A 、when the train leaves B、if the train had left C······

问题描述:

1、Could you make sure---------- ? A 、when the train leaves B、if the train had left C······
1、Could you make sure?
A 、whenthetrainleavesB、ifthetrainhadleft
C、whenthetrainwouldleaveD、wherehasthebusgone

A.
这里could表示委婉的语气,并不表示过去式,因此选择A.
B中had left 没有使用过去完成时的道理,C would应该是will,D没有这种说法.