[单选题]
Your motorboat can mov xbv2aw*f,)b (w- yf 8omn0aozxkj c7pv6yc009 ri x0ve at 30 km/h in still water. How much time will it take you to move 12 km downstrekj0p0 civ6 r7xx0 cy9zam, in a river flowing at 6.0 km/h?
A. $20 \; min$
B. $22 \; min$
C. $24 \; min$
D. $30 \; min$