[单选题]
Your motorboat can move at 30 km/h in still water. xmut60)y --p + (vpao8yb8im m2gf;yzi/powsHow muchdvchj.n ncm+;t052lb+l +ko a time will it take you to move 12 km downstream, in a river flowing at 6.0 km/h 2ln0 hmkl ;+v+c.dj5caon+bt?
A. $20 \; min$
B. $22 \; min$
C. $24 \; min$
D. $30 \; min$