下列条件能判断两个三角形全等的是(      )
①两角及一边对应相等     ②两边及其夹角对应相等 
③两边及一边所对的角对应相等   ④两角及其夹边对应相等

根据文章内容，选择正确的答案。
   New York，London，Paris and other big cities are exciting places to live in. There are many interesting things to see and to go to. You can go to different kinds of museums，plays and films. You can also buy things from all over the world.
   But there are some problems in big cities too. It is expensive to 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.
   But sometimes these people can't find work or a good place to live in. Also it is hard to keep the cities safe(安全的）and clean.
   Some people enjoy living in big cities，others do not. Before moving to a big city，they should think about the problem of living there.