It’s difficult for such a girl to swim ________ the river. [ ]

Have you seen _____ empty box?— Do you mean _____ box you showed to me yesterday? I put it in your schoolbag.

Xu Qian is a funny girl. She loves to __________ jokes.

I’m interested_____ flying kites.[ ]

A: Alice, please tell Eric to call me when he _________ back. B: No problem.