[单选题]
A boat can move at 30 km/h in still waqb33 5qvw 0xrz u k*l0onqoc,0ter. 3,hc/mpe 8mjm(iv v/47moqg k How long will it take to move 12 km upstream in a river flowing 6.0 km/h?8 7(vvpgmhm3 /,imj4e m ok/cq
A. $20 \; min$
B. $22 \; min$
C. $24 \; min$
D. $30 \; min$
