drivers --- wear the safety belt when driving this is the traffic rulea\ canb\ mayc\ willd\ must说理由!

drivers --- wear the safety belt when driving this is the traffic rule
a\ can
b\ may
c\ will
d\ must
说理由!

正确的答案是 d\ must
must 必须
must wear the safety belt 必须系上安全带

选D D项表示必须之意