the reason引导的从句什么时候用because什么时用thatthe reason why he was late was__he was caught in heavy traffic

the reason引导的从句什么时候用because什么时用thatthe reason why he was late was__he was caught in heavy traffic
the reason引导的从句什么时候用because什么时用that
the reason why he was late was__he was caught in heavy traffic

the reason引导的从句什么时候用because什么时用thatthe reason why he was late was__he was caught in heavy traffic
the reason why he was late was that he was caught in heavy traffic
这边是一句定语从句套上表语从句
【the reason why he was late】定语从句
【was that he was caught in heavy traffic】是一句表语从句
表语从句只能用that引导的