The Liskov Substitution Principle is a fundamental concept in object-oriented programming, ensuring that derived classes can be used in place of their base classes without altering the correctness of the program.

Every piece of plastic we produce should have a clear path to reuse or recycling.

We are not interested in the spectacular. We are interested in the specific.

人只有在处于依赖状态的时候才是柔弱的，如果他无拘无束，不依赖他人的话，他早就是很强壮的了。

钢铁的未来在于回收和减少碳排放。