【题目】—Look at these tracks. It ________ be a wolf. I’m sure about it.
—You are right! We have to be careful.
A.mayB.mustC.can’tD.shouldn’t
在线课程【答案】B
【解析】
考查情态动词。句意：——看这些脚印。一定是一只狼。我敢肯定。——你是对的!我们必须小心。A. may可能；B. must一定；C. can’t不能；D. shouldn’t不应该；应该不会。根据下文I’m sure about it.可知为肯定的猜测。故选B。