as black as coal

例句：

1. 1. The coal mine is located in the heart of the mountain range.
   煤矿位于山脉中心。
2. 2. The coal mine has been closed due to safety concerns.
   由于安全问题，煤矿已经关闭了。
3. 3. The coal miners are exposed to dangerous conditions every day.
   煤矿工人每天都面临着危险的工作环境。