goes swimming是一个动作,所以疑问词用what.所以答案就是：
What does Millie do by bus twice a week?1.Millie is good at swimming.(对swimming提问）2.Miilie wants to go swimming.（对go swimming提问）3.1.Millie goes swimming by bus twice a week.对（Millie）提问怎么写答案分别是：What is millie good at？what does millie want to do？who does go swimming by bus twice a week?