里氏替换原则是面向对象编程中的一个基本概念，确保派生类可以替代其基类使用，而不会改变程序的正确性。

Every great and deep difficulty bears in itself its own solution. It forces us to change our thinking in order to find it.

The future of steel lies in its ability to adapt to a low-carbon economy.

遗忘就是自由。

除非某处的某人宁愿你不做这件事，否则这件事就不值得做。

The greatest happiness of life is the conviction that we are loved; loved for ourselves, or rather, loved in spite of ourselves.

一点真诚带有危险，真诚过渡就绝对致命。