[求助]OG10-49?

pangpangshin

49. A milepost on the towpath read “21” on the side facing the hiker as she approached it and “23” on its back.
She reasoned that the next milepost forward on the path would indicate that she was halfway between one
end of the path and the other. However, the milepost one mile further on read “20” facing her and “24” behind.
Which of the following, if true, would explain the discrepancy described above?
(A) The numbers on the next milepost had been reversed.
(B) The numbers on the mileposts indicate kilometers, not miles.
(C) The facing numbers indicate miles to the end of the path, not miles from the beginning.
(D) A milepost was missing between the two the hiker encountered.
(E) The mileposts had originally been put in place for the use of mountain bikers, not for hikers.

这道题目不是特别理解意思,希望朋友们能帮忙解释下,谢谢~

will_kk

一个人,走在路上,看到个牌牌,正面21反面23,预期下个牌牌是22,22.结果走了一段,发现是20,24

问:咋回事?