I don't know the reason why he was absent yesterday.reason后面

I don't know the reason why he was absent yesterday.reason后面 John was absent from class yesterday.i don't know his reason I don't know the reason why he did't come to the meeting yes I don't know __.A.the reason why can be B.why the reason may I don't know the reason ______you were absent from the meeti I don't know the reason ____ you were absent from the meetin I don't know the reason -------- he cried Athat Bwhy I don’t know the reason why he said these words.里面的why引导的从句是 The reason why he was absent from the meeting was that his c The reason why he didn’t attend the meeting is that he was i I dont know the reason why he was late 为什么不用that The reason why I was sad was that he didn't understand me.