what happens during lunch time What's happening outside?

问题描述:

what happens during lunch time What's happening outside?
为什么第一句的 happens 要加s,但我知道问句里动词一定要变原形.像是 what happen during lunch time 第二句What's happening outside?为什么这可以用助动词is,那what happened to you?为什么不能用what did happed to you?

我问:what happens during lunch time?为什么可加S,问举中动词不是要变原型?

what happens during lunch time 是将来时
what's happening outside?是现在时