没有what's happen,但有what's happened或what's happening
what happened曾发生过什么?
what's happened已经发生了什么?
what's happening正在发生什么?能不能讲讲happen的其他用法please,thank you.（最好再加点例句）1.发生 It happened under my eyes.这事就发生在我眼皮底下。2.产生结果, 发生作用 He pressed hard on the brake but nothing happened.他使劲往下踩刹车, 但没有发生作用。3.碰巧, 恰巧 What would happen if your parents found out?如果你的父母发现了, 会怎样呢?It happens that he is a teacher of English.恰好他是个英语教师。