[单选题]
A boat can travel 4.0 s;nxup3yy) 6 /axys t(m/z wc(; (: xkp6ytpdh l*5/qrvds in still water. With what speed, relative to the shore, does it move in a riveywdl(p 6: p /(5d;chv zrqk*txr that is flowing at 1.0 m/s if the boat is heading straight across the river?
