A、There are many visitors there. B、There are many students there. C、There are many old streets there. D、There are many bicycles

Cambridge is about 90 kilometers northeast of London. It is one of the most beautiful places in Britain. Everything about the city of Cambridge reminds you of its famous university: students on bicycles, the atmosphere of learning, traditions and the magnificent buildings of the 30 colleges that are in the University of Cambridge. Most of the colleges stand on the bank of the River Cam, the gentle river that flows through the heart of the city.[19]Tourists and students like boating in a kind of flat-bottom boat to see the colleges or to relax. If the water traffic reminds the visitor of Venice,[20]the road traffic is more likely to recall Beijing or Amsterdam. The streets are full of bicycles, hundreds and hundreds of them. They provide a cheap form of transport for the students and a very convenient way of getting around Cambridge’s nearer streets.
19. What do tourists enjoy doing in Cambridge for relaxation?
20. Why did the road traffic in Cambridge remind one of Beijing?
21. What is the speaker’s impression of Cambridge?