Which form of coal has the highest carbon content in it?
(a)- Lignite
(b)- Sub-bituminous
(c)- Bituminous
(d)- Anthracite

Hint: The successive stages in the transformation of vegetable matter into coal are- wood, peat, lignite, sub-bituminous, bituminous, steam coal, and anthracite. The purest form of coal contains 95% of coal.

Complete answer:
Coal is a highly carbonaceous matter that has been formed as a result of the alteration of vegetable matter (e.g. plants) under certain favorable conditions. It is chiefly composed of carbon (C), hydrogen (H), nitrogen (N), and oxygen (O) besides non-combustible inorganic matter.
The successive stages in the transformation of vegetable matter into coal are- wood, peat, lignite, sub-bituminous, bituminous, steam coal, and anthracite.
Peat is not considered as coal.
Lignite- It is also called brown coal and it is the dirtiest coal. It is used for power generation.
Sub-bituminous- It is used for steam-electric power generation. It is also used as a source of light aromatic hydrocarbon for chemical synthesis.
Bituminous- It is a dense black rock but sometimes it is dark brown. It is used as fuel in the power station. It is also for making coke.
Anthracite- It is black coal which is harder and has a glossy appearance. It can burn for a longer time and it has 85 – 95% carbon in it.
Hence the correct answer is an option (d)- Anthracite

Note:
The percentage of carbon in peat is 40-55%. In lignite 55-60% of carbon is present. In bituminous, the percentage of carbon is 40-80%. The anthracite carbon is found only in Jammu and Kashmir and that too in small quantities.