— How long does it take to get there?—A. 20 kilometersB. 3 milesC. About a quarterD. 20 mi

问题补充：

— How long does it take to get there?—

A. 20 kilometers

B. 3 miles

C. About a quarter

D. 20 minutes’ walk

答案：

A. 20 kilometers

B. 3 miles

(答案→)C. About a quarter

D. 20 minutes’ walk

解析：how long 多久，提问时间长短，故选C，大约十五分钟。