"What's up?"、"What's going on?"、"What's happening?" 这三种表达方式都可以用来询问什么事。
"What's up?" 起源于青年人的俚语，是问候语中最常用的句型之一。它可以表示问候、关心他人，也可以表示对事情的询问。
例句："Hey, what's up?" "How's it going? What's up?"
"What's going on?" 可以表示对当前事情的询问，也可以表示对某种情况的关注。
例句："Excuse me, what's going on here?" "I heard some noise outside, what's going on?"
"What's happening?" 同样可以表示对当前情况的询问，强调事情正在发生。
例句："What's happening? Why is everyone so excited?" "Can you tell me what's happening here?"