Why did you decide to be a biology major? 这句话怎么解释?major在句中的意思是什么?

Why did you decide to go to college? Why did you decide it so fast? why people like to think more ? Why did you decide on Beijing for vacation?为什么用介词on 一Tom,can you tell me －Sorry,I don’ t know.A.how many people have been here B.when is the meeting C.why did they decide to do it.我觉得AB都可以呢, Why did you decide to be a biology major? 这句话怎么解释?major在句中的意思是什么? really don't understand why you did that? Why don't you pretend like we did?怎么翻译? why did you miss Why did you leave why did not you why did you not work 和why didn't you work意思一样吗 why did you tdlk like Why did you leave me why did you say goodbye why did you let it why did you do it Why did you do it? Know you can't mind,why did i just won't open翻译