happen与happens的区别

what happen与what happens的区别是什么? happen,happens与happened三者区别? 关于no matter what happens与happen happen to 与happen to have done 的区别是什么? where happens something?Where does something happen?有什么区别 happen,take place与occur 的区别 take place与happen的区别! take place与happen的区别 happen与take place 的区别 happen与come about的区别 happen与take place的区别 请问What happens?与What happening?的区别?