自然实验可以为经济问题提供有价值的见解。
Natural experiments can provide valuable insights into economic questions.
煤炭曾是工业进步的支柱，但其未来必须平衡经济需求与环境责任。
When I was in college， I wanted to be involved in things that would change the world.
Every performance is a new opportunity to touch someone’s heart.
Education is an ornament in prosperity and a refuge in adversity.
做你自己，因为别人都已经有人做了。