[单项选择] London Cabbies(出租车司机) Every city in the world has taxis to take tourists to interesting places.London is the only city in the world where taking a taxi is an （51）experience for tourists.This is partly because of the special black cabs,which are found in no other country.But it is also because of the drivers themselves.（52）British people are famous for being polite and reserved,London cabbies are well-known（53）their willingness to talk. Some customers say that once the door shuts and the cab（54）off they are a captive(监禁了的)audience.It is impossible to get the taxi driver to stop （55）.“They’re self-confident and free thinking,”said Malcolm Linskey,the author of a history of taxi drivers in London. They are also expensive.London has the most expensive taxis of any city in the world except Tokyo.That’s why Ken Livingstone,the Mayor of London,is planning to make taxi drivers negotiate their fares with（56）before they take a ride. Drivers agree that their fares are ex
A. for
B. as
C. of
D. at