问题补充：
—Mum,I watch TV now ?
—No, you finish your homework first.
A. may, need
B. can, have to
C. do, must
D. may , must
答案：
A. may, need
(答案→)B. can, have to
C. do, must
D. may , must
解析：句意: -妈妈，现在我可以看电视吗？-不，你必须先完成你的家庭作业。may 或can 可以表示征求别人的许可；need 需要；have to 必须，不得不；must 必须；根据句意可知选B。
