請依下文回答第 46 題至第 50 題\nLondon is one of the top travel destinations in the world, but for a first time visitor, navigating this large city can be overwhelming. Using an Oyster card is an easy way to save time and money if you are planning to use public transportation in London. An Oyster card is a blue credit-card-sized contactless smartcard that can be used on every form of public transportation within London, including public bus, underground, railway, and some river boat services. \nThe Oyster card was first issued on June 30, 2003. The name was decided after a lengthy discussion. Two other proposed names were “Pulse” and “Gem.” “Oyster” was chosen because it sounded like a fresh name that was not directly linked to transportation; also, the hard shell of an oyster and the concealed pearl symbolize security and value. But perhaps the best reason is William Shakespeare’s quote “ The world is your oyster,” which means one has the ability and freedom to do anything or go anywhere. So far more than 60 million cards have been issued and over 85% of rail and bus travel in London is paid by using an Oyster card. The card never expires. It can be used after any length of time. Besides, deposits can be refunded on return of the card. \nThe best reason to get an Oyster card is cost savings and convenience. It is cheaper to travel in London with this card than it is to purchase individual paper tickets for each trip. The card allows 40 people to pass through a ticket gate per minute, 15 more than with paper tickets, and also makes boarding a bus three times faster. For London Underground and the railway system, passengers have to touch the card on an electronic reader when entering and leaving the transport system. The reader will show either a green or a red light. The former indicates that you have sufficient credit for your journey while the latter indicates you do not have enough credit and you have to purchase more credit before you can continue your journey. For the public bus service, which has fixed price, passengers only need to touch the reader at the start of the journey when boarding. If you touch the reader again when you get off the bus, you will be charged an additional fare.