-There is a lot of smoke coming out of teaching building there.--Really?It_be a fire,most probably

-There is a lot of smoke coming out of teaching building there.--Really?It_be a fire,most probably

ought to
问：教研楼里冒出很多烟
答：是么?应该是起火了,很有可能.
can 可以是 ,语义不通
ought to 应该是 可能性较大
may 也许是,可能性较小
must 一定是,如果选D ,后面就不应该再说 most probably ( 很有可能了）

IS
it is a fire失火了

-There is a lot of smoke coming out of teaching building there. --Really?It may be a fire,most probably