A、From tram to trolleybus to Routemaster. B、From trolleybus to Routemaster to red bus. C、From trolleybus to Routemaster to moder

Today is a rather sad day for one of the London’s oldest friends. The famous red London bus, officially called The Routemaster, is being replaced by modern buses. Like Big Ben, Buckingham Palace and the red telephone box, the red bus has listed one of these heritages.
    They first arrived on London’s streets in 1959 to [16]replace the trolleybuses, which were powered like a tram by overhead electric cables. In fact, my father used to drive trolleybuses and went on to drive the new red bus when they arrived almost 50 years ago. Later on, it was always a special treat for me to go to work with my dad to see all the sights of London. And it became such a star that it was even featured in Britain’s first Elvis Presley type film Summer Holiday starring Cliff Richard.
    But some people aren’t sad to see the back of the famous red bus. They believe Routemasters are no longer a suitable form of transport for London. 10% of Londoners can’t even get onto it: old people, disable people, people with buggies. It’s a real, real problem. The hop on, hop off platform at the back of the Routemaster bus makes it a convenient form of transport for passengers. [18]But sadly, such features also make the bus dangerous. As some research shows, people are 5 times more likely to have an accident on a Routemaster than on any other sort of bus.
    After today, we can see only a few Routemasters on the Heritage Routes, special journeys that will mostly be taken by tourists.
16. According to the speaker, what is the evolution of London’s public transport?
17. What makes the Routemaster famous?
18. What is the disadvantage of Routemaster?