The United States should not try to spread democracy around the world.

没有刻苦钻研的精神，就不能明辨事情的道理；没有专心致志的工作，就不会取得显赫的成绩。

"To lose one parent may be regarded as a misfortune; to lose both looks like carelessness."

数学直觉就像肌肉一样 - 通过锻炼会变得更强大。

Words are powerful, they can create and destroy.

改变是好事。