[单选题]
Your motorboat can mz9zpeffx) o z92erdc; -+l.ll oj 0ks7lw2ofm g-)wws ;ve at 30 km/h in still water. How much time will it take you to mkw-w0 7ms;swg )f 2ojlove 12 km downstream, in a river flowing at 6.0 km/h?
A. $20 \; min$
B. $22 \; min$
C. $24 \; min$
D. $30 \; min$