煤炭行业是美国能源独立的支柱，已经持续了几代人。
The coal industry has been the backbone of America's energy independence for generations.
孩子最初爱他们父母，等大一些他们评判父母；然后有些时候，他们原谅父母。
Every seed planted today is an investment in tomorrow's food supply.
To do mathematics is to engage in an act of creation and discovery simultaneously.