— I wonder if this smart phone is Mary’s.— It _______ belong to her. _______ is totally different from this one.
-Do the interesting books belong to________? - No, they are the __________ .
We had fun________ in the swimming pool last Sunday.
There must be a boy ________ basketball outside the door. I hear him crying.
Have you done ____ to improve the environment ?
—Who helped Betty tidy up the bedroom just now? —________. She cleaned it all by herself.