WhileIwentsightseeinginLondon,IvisitedtheLondonUndergro...
问题详情：WhileIwentsightseeinginLondon,IvisitedtheLondonUnderground.Likemosttourists,Iwasveryinterestedinitasitisthe 61 (old)systemintheworld.Itisalsoverycomplex.Iwastoldthatthefirstpartoftheunderg...