I happened to check out videos

I happened to check out videos I’d better ______ my luggage quickly or I’d miss my flight.1.to check 2.check 3.to check in 4.check I’ll get someone to check it right now为什么这里check前要加to I have to check in to my hotel I happened to pass by,so I dropped in I really don't know what____him last night.A.happened with B.happened to C.has happened to D.has happened with I'd like to check in翻译成中文 i would like to come and check on you babe Happened to /happened with 区别 it happened that i blabla.怎么换成带happened to的结构? I wanted to know_to him.为什么填what happened而不是what has happened? 翻译:I happened to be at the station ,when it happened I don’t know what ___ last night.用he happened 还是happened to him 为什么 I don't know what___(happen)to him 为什么填的是has happened 而不是happened I don't know what___(happen)to him 为什么填的是has happened 而不是happened I still don't know what____to him.He ought to come now.(回答时告诉我为什么 A.had happened B.was happened C.has happened D.happened I do want to know what really happened.翻译 It happened _______(rain) when I went to see him