why引导的原因状语从句：
Please tell me the reason why you didn't come to school yesterday.
that引导的原因状语从句：
that引导原因状语从句通常和now连用，即：now that 表原因，如：
Now that you are a middle school student, you may probably spend more time in reading
原因状语从句指在句中用来说明主句原因的从句。引导原因状语从句的从属连词有because（因为）, as（由于）, since（既然）, now(that)（既然）, when（既然）, seeing (that) （由于，鉴于）, considering (that)（考虑到）, for（为）, given (that) （考虑到）等。
