[单选题]
A boat can travel 4.0 -u j -e1fk;savm/s in still water. With what speeggf70 i2 lw s8 nx3uh-xmmhm63d, relative to the shore, does it move in a rivers fhg u6x 3m-h8i0lmm7w xn2g3 that is flowing at 1.0 m/s if the boat is heading straight across the river?
