题目选项分析

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?

【选项】The mileposts had originally been put in place for the use of mountain bikers, not for hikers.