---- 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

发生人畜共患病时，除立即报所在部门实验室生物安全管理委员会外，还必须立即报当地卫生防疫部门，采取紧急措施，防止疫情蔓延。