Handy measure: the distance between your fingertips of your outstretched arms at shoulder level is your height.

I think prime numbers are like life. They are very logical but you could never work out the rules, even if you spent all your time thinking about them.

On earth there is nothing great but man；in the man there is nothing great but mind.

解释：割地给秦国（来求得暂时的安稳），就好像抱着木柴救火一样，木柴烧不不完，火就不会灭。