煤炭行业是美国能源独立的支柱，已经持续了几代人。

我总是尽力做到最好，但这并不容易。

Learning is any change in a system that produces a more or less permanent change in its capacity for adapting to its environment.

渔业真正的领导力意味着在经济需求和环境责任之间取得平衡。