Question

—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

Answer 1

B?

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。