In international trade, a country should specialize in the production of goods for which it has a comparative advantage, and trade with other nations to maximize overall economic welfare.

解释：不通过学习而能自己知道的，不去请教他人而能自己通晓的，从古到今没有这样的事。

"Every civilization is built on the bones of another."

年轻时，你以为长大后就会幸福。但长大后，你意识到年轻时的自己才是幸福的。