—There is a lot of smoke coming out of the teaching-building there.—Really?It be a fire

问题补充：

—There is a lot of smoke coming out of the teaching-building there.

—Really?It be a fire,most probably.

A. can

B. ought to

C. have to

D. must

答案：

A. can

(答案→)B. ought to

C. have to

D. must

解析：考查情态动词。由most probably可知说话人的语气并不非常肯定，所以用ought to表示推测，语气比must弱一些，给自己留有一些余地。