单选题Questions 8-10 are based on the following monologue.
单选题
It is easy for the visitors to travel by tube in London because of ______.
【正确答案】
C
【答案解析】[听力原文]
Traveling on the London underground (the "tube") presents few difficulties for visitors because of the clear color-coded maps. It is always useful to have plenty of spare change with you because there are often long queues at the larger stations. If you have enough change you can buy your ticket from a machine. You will find signs which list the stations in alphabetical order, with the correct fares, near the machines. There are automatic barriers which are operated by the tickets. You should keep the ticket, because it is checked at the destination.
单选题
It"s good to have spare changes at hand because ______.