don't give up the hope no matter what happens为什么happen必须加s?

don't give up the hope no matter what happens为什么happen必须加s?
don't give up the hope no matter what happens
为什么happen必须加s?

don't give up the hope no matter what happens为什么happen必须加s?
no matter what 引导让步状语从句,what相当于主语,后面谓语用三人称单数形式

what 这里是不可数，所以后面happen要加s 单数形态