问题
选择题
—Why was he late for school yesterday?
— He overslept. By the time he got to the bus stop, the bus ________ already ______.
A．has; left
B．had; left
C．was; leaving
D．have; left
答案
答案：B
题目分析：句意：昨天他为什么迟到了？——他睡过头了。他到达公交车站时，公交车已经开走了。结合语境可知下文描述的是一直持续到过去某时的动作，故用过去完成时态，选B。