New York, London, Paris and other big cities are exciting places to live in. There are many interesting things to see and to do, you can go to different kinds of museums, plays and films. You can also buy things all over the world.But there are serious problems in big cities, too. It’s expensive to live there, and there are 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 receive good medical care. But sometimes these people cannot find work or good places to live in. Also it is hard to keep the cities safe and clean.Some people enjoy living in big cities; others do not. Before they move to a big city, they should think about the problems of living there.题In big cities people can_____ .
选项：

A: buy things all over the world
B: live easily without working
C: sing songs everywhere
D: live without any problems