题目内容：

" what is happening?" she asked.为什么是is happening.

优质解答

你好.用" what is happening?",说明she对正在发生的事情感兴趣,尽管she也可以说“what has happened?”-------这说明she对已经发生的事情感兴趣.
1 what is happening = what is going on
2 what has happened = what do you know that has happened