When the students came into the room,the teacher__on the blackboard.应该填什么时态A,is writing B,was writing C,wrote应该选哪个,为什么
问题描述：
When the students came into the room,the teacher__on the blackboard.应该填什么时态
A,is writing B,was writing C,wrote应该选哪个,为什么
答
is
答
因为前面用的是came,所以后面应该用过去式was.
答
B,前面When引导的从句是过去式