Which is the coal with the highest energy available per unit to burn: lignite, subbituminous, bituminous, or anthracite?

Anthracite

Explanation:

Anthracite produce highest amount of energy than other. It contain 86-97 percent carbon. Bituminous coal contain 45-86 percent carbon.

Subbituminous cola have 35-45 percent carbon while lignite contain 25-35 percent carbon.

Coal is source of many organic materials. It is fossil fuel and form after long period decay of plants. It is formed when trees are buried under earth

about 500 million years ago. The chemical and bacterial reactions take place and plant wood converted into the peat.

Than because of high temperature and pressure inside the earth peat is converted into the coal.

Through other processes it is than used to make the fuels such as coke. coal tar and coal gas.

Coal tar is the source of many organic compounds which are separated through fractional distillation.

About 80% of coal in Pakistan is used to bake the bricks and also used in lime kilns and for domestic purpose.

the answer would be a