The correct answer is (a) Anthracite.
Anthracite is the purest form of coal. It is a hard, black coal with a high carbon content. It is the most expensive type of coal to mine and transport, but it is also the most efficient to burn. Anthracite is used in power plants to generate electricity and in industrial processes to produce heat.
Bituminous coal is a soft, black coal with a high carbon content. It is less expensive to mine and transport than anthracite, but it is not as efficient to burn. Bituminous coal is used in power plants to generate electricity, in industrial processes to produce heat, and in the production of steel.
Lignite is a brown coal with a low carbon content. It is the least expensive type of coal to mine and transport, but it is also the least efficient to burn. Lignite is used in power plants to generate electricity and in industrial processes to produce heat.
Peat is a soft, brown material that is formed from the remains of plants that have been buried and subjected to heat and pressure over time. It is not a true coal, but it is sometimes referred to as “brown coal.” Peat is used as a fuel in some parts of the world, but it is not a major source of energy.