单选题 I have rung the door bell for five minutes, but no one has come to open the door. The Browns ______ out.
  • A. should be
  • B. would be
  • C. can be
  • D. must be
【正确答案】 D
【答案解析】[解析] 根据前文，此处应是比较肯定的推测，而英语中使用must这一情态动词来表示推测，故选D)。