Can you tell me what to wear at the party—If I you, I the blue jeans.

I reallydon’t know _________ I had my money stolen.

下列各句中，加横线的成语使用正确的一项是（ ）

Mary spends two hours ______ her homework every day.

— Is there any possible way to help the children get rid of such a bad habit? — To be honest, it’s very hard, but we ____ on this problem. [ ]