— How could they keep us waiting for so long?
— They got on the bus half an hour ago and they be here in ten minutes, I think.
A. might
B. would
C. should
D. must
网友回答
A. might
B. would
(答案→)C. should
D. must
解析：考查情态动词。句中should表示“应当”之意：——他们怎么能让我们等这么久呢？——他们半个小时前上公共汽车，我想他们应当10分钟内到达这里。