---Listen! The fire engine is roaring! (消防车吼叫)
--- Oh, there be a fire somewhere. How terrible!
A. should
B. must
C. have to
D. will
网友回答
A. should
(答案→)B. must
C. have to
D. will
解析：情态动词辨析。A. 应该 B. 必须；一定 C. 必须；不得不 D.愿意。句意：听！消防车正在鸣叫。——哦，一定是有地方发生火灾了。太可怕了。Must强调主观判断的肯定，have to强调由于客观情况的被动动作，结合语境可知选B。