Who can afford to do professional work for nothing?

智能化开采是煤炭行业高质量发展的关键。

An excellent man; he has no enemies; and none of his friends like him.

"The world is full of signs, but we are often too blind to see them."

这世界是个好地方，值得为它奋斗。

我认为最好的学习方法就是实践。

You have enemies? Good. That means you've stood up for something, sometime in your life.