[单选题]
A boat can travel 4.0 .peu,* /wfhru0 g. yxogj)f y6m/s in still )qljj:0vbx7sz w(o 1xqb 4ejfz -pq1) water. With what speed, relative to the shore, does it move in a v4)j1z:bw1 7b0(jz ojqxx)fpleqq- sriver that is flowing at 1.0 m/s if the boat is heading upstream?
