Read the flowing passage and choose the best answer from the four choices marked A, B, C and D. The London Underground (usually called "the Tube") is the biggest subway system in the world. It is also the fastest way to travel in the city. The network consists of nine major routes called "lines". You can buy tickets at any underground station, at a ticket office, or from a ticket machine. Some of the ticket machines require exact money. All of the machines display "Change given" or "Exact money only" signs. The price of the ticket depends on the length of the trip. The longer the tip is, the higher the cost of the ticket. Trains stop at all stations. On some trains, passengers need to press a button to open doors. Every underground train has maps that show all the stations on the line you are traveling on. There is a map of the whole underground system in every station. Smoking is not allowed on underground trains or in stations1. According to the passage, the other name of the subway in London is "____".A. the subway systemB. the routesC. the underground systemD. the Tube2. You can buy tickets at some places except ____.A. a ticket officeB. a ticket machineC. the underground stationD. outside the station3. On some trains, if a passenger wants to get off, he should ____.A. inform the driverB. press a buttonD. press the doorC. show his ticket4. A map of the whole underground system can be found in ____.A. every trainB. each stationD. some ticket officesC. some train5. This passage mainly tell the reader how ____.A. the London Underground worksB. the London Underground developsC. a passenger buys a subway ticketD. a passenger travels on the Tube