when he got home ,his parents _.were sleep were asleep are sleeping

问题描述:

when he got home ,his parents _.were sleep were asleep are sleeping
为什么?

were sleeping.当他回家时他的父母正在睡觉.用过去进行时.从上面三个答案中选were asleep.sorry.when引导的是过去式后面也应相应用过去式。