[单选题]
A boat can travel 4.r,z6 f;d s:mvg9qf,iv0 m/s in stlhlo a ed.wubp, 1l+yy ih1hv 2k)w):7ill water. With what speed, relative to the shore, does it move in a river that is flowing at 1.0 m/s if the boat is heading upsh7) 1, wek:l u)h+hl12aioypy.bvw l dtream?
