The concept of probably approximately correct (PAC) learning has been foundational in computational learning theory.

每个故事至少有两面。

球场上最强大的武器是你的头脑。

教师的爱是滴滴甘露，即使枯萎的心灵也能苏醒；教师的爱是融融春风，即使冰冻了的感情也会消融。