[单选题]
A boat can travel 4.0 m/s in fk w-,a h*cov8still water. With whzaz + y,/m,x8u isqlhb3qq9 c.at speed, relative to the shore, does it move in a river thatbi8zylc9,qq sh.z +xa qum3 ,/ is flowing at 1.0 m/s if the boat is heading straight across the river?
