—Can we run across the road now?—No,we _ .We have to wait un
—Can we run across the road now?—No,we _ .We have to wait until the light turns green.为什么B
—Can we run across the road now?
—No,we _ .We have to wait until the light turns green.
A.needn't B.mustn't C.couldn't D.shouldn't
为什么选B,can't行不行?