下列词语中加线的字，每对读音都不相同的一组是(　　)

How did you know the surprising news—– I happened _______ the event then.

There is______ art room in the building.

(2014·宝鸡三检)By the time the girl comes back to life，scientists probably________a cure for this incurable disease

Only after her mother came to help her for the first few months _____ to begin her propjet.