Which of the following types of coal has the highest energy content and produces the fewest polluting chemicals?

Anthracite: The highest rank of coal. This coal is hard, brittle, and black lustrous. It is often referred to as hard coal, containing a high percentage of fixed carbon and a low percentage of volatile matter. It has the highest carbon content, the fewest impurities, and the highest energy density of all types of coal and is the highest ranking of coals.

Explanation: There are four ranks of coal

Coal rank measures the carbon content which is in correlation with calorific value and metamorphic grade. It has a very high carbon (over 90%) and low volatile content (below 5%) 1.