He said that he dropped his bag when he ______ for the bus.

He said that he dropped his bag when he ______ for the bus.
A、was runing
B、was running
C、were running
D、is running
【正确答案】：B
【题目解析】：考察when 引导的时间状语从句，根据dropped 可判断，从句动词需变成过去式，排除D。He 为单数，be 动词为was ,排除Crun 加ing 时要双写n , running。