Explanation
Coal is a naturally available substance whereas Coke is prepared substance with some impurities and high Carbon content, usually made from Coal.While Coal is Solid mass in physical appearance, Coke is Porous ( it means that it has large surface area ).
So the density of coal is more than the coke as coke is porous which has large surface area.
Hence option A is correct.
Coke is used in the preparation of water gas ($$CO+H_2$$), producer gas ($$CO+N_2$$) and graphite by artificial methods.
$$C+H_2O\longrightarrow CO+H_2$$ ..... (water gas)
$$C+air\longrightarrow CO+N_2$$. ..... (producer gas)
Hence, option $$D$$ is correct.
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