We knock _____people’s doors, and they usually give us some candy _____ a treat.

A. on, to           B, at, to           C. on, as           D. on, on

Please knock _______ the door before you come in.

1. A.
   at
2. B.
   in
3. C.
   to
4. D.
   of

We knock _____people’s doors, and they usually give us some candy _____ a treat

1. A.
   on, to
2. B.
   , at, to
3. C.
   on, as
4. D.
   on, on