We ________ eat in the classroom, because it's impolite(不礼貌) to the teachers.

1. A.
   can
2. B.
   can't
3. C.
   need
4. D.
   must

 We _______ eat in the classroom, because it’s impolite (不礼貌) to the teachers.

   A. can          B. can’t          C. must            D. need