你付出的能量就是你得到的能量。

The only power any government has is the power to crack down on criminals. Well, when there aren't enough criminals, one makes them. One declares so many things to be a crime that it becomes impossible for men to live without breaking laws.

让它简单。让它难忘。让它吸引人。让它读起来有趣。

地球是一个动态的行星，其内部热量是地质变化的驱动力。

学习数学的唯一方法就是做数学。