问题补充:
---Dad, must we wait until the light becomes green?
---Yes, I’m afraid we . That’s the traffic rule.
A. can
B. may
C. have to
D. need
答案:
A. can
B. may
(答案→)C. have to
D. need
解析:must的含义是必须一定,其否定形式mustn’t表示禁止的含义。故must的否定回答一般借助于needn’和don’t have to来构成,句意:爸爸,我们必须等到绿灯亮了吗?——是的,恐怕我们必须这样做。这是交通规则。结合语境可知选C。