Listen to the passage and fill in the blanks with the missing words.[音频]New York, London, Paris and other big cities are places to live in. There are many interesting things to see and to do. You can go to different kinds of , plays and films. You can also buy things from all over the world.But there are serious problems in big cities, too. It isto live there，and there are too many people in some places of big cities. Every year many people move to the cities to find jobs, to study at good schools and to receive . But sometimes these people cannot find work or a good place to live in. Also it is hard to keep the cities .Some people enjoy living in big cities, while others do not. Before people move to a big city，they should think about the problems of living there.