Correct Answer: lignite

Solution : The correct option is Lignite.

Lignite is often referred to as brown coal because of its brownish-black color and relatively low carbon content compared to other types of coal like bituminous or anthracite. It is considered the lowest rank of coal in terms of carbon content and energy density. Lignite is formed from peat under the pressure of sedimentary rock and is typically used for electricity generation in power plants.