Are you happy ________ your English study?—Yes, I think so.[ ]

Have you ever been to Shanghai, Mary?—Yes. I ___________ there three times.

I think it’s going to be an argument.（争论）—Yes, it could be.—I wonder ______we can do .

We are going to have _________off next month, so we will go on a trip.

I like your pet dog very much. But I can’t find _______ in the pet shop. Where did you buy _______?