地球是一个动态的物体，其表面在不断变化。
If you aren't in over your head, how do you know how tall you are?
不同文化之间的对话不仅是可能的，而且是人类进步的必要条件。
Sustainability isn't an option—it's a necessity for the future of our industry.
There is nothing which I dread so much as a division of the republic into two great parties, each arranged under its leader, and concerting measures in opposition to each other.