[单选题]
A boat can travel 4.0 m/s in s70 s6v*cvgk 1 ry(hf/(lwd jwftill water. With what sofpk( g,i55bt*y zz+e peed, relative to the shore, does it move in a river that is flowing at 1.0 m/s if the boat is headipt( ozze5i*g 5 kfy,b+ng straight across the river?
