作为经典力学的先驱，伽利略在实验的基础上运用____的方法，正确地揭示了：力不是维持物体运动的原因，而是____物体运动状态的原因。

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.