每一种化合物都必须有确定的组成，这可以用其元素的符号来表示。

The most powerful force in the universe is compound interest.

The most elegant proofs are those that reveal the heart of the problem with clarity.

The challenge of our time is to create a sustainable energy future.

Life is too short to wake up with regrets. So love the people who treat you right, forget about the ones who don’t, and believe that everything happens for a reason. If you get a chance, take it. If it changes your life, let it. Nobody said life would be easy, they just promised it would be worth it.

种一棵树最好的时间是20年前，其次是现在。