Coal with the highest carbon content is obtained from the organic matter through a number of steps under some atmospheric factors as follows:

Wood  $\underset{\mathrm{Y}}{\overset{\mathrm{X}}{\to }}$ Peat $\underset{\mathrm{Y}}{\overset{\mathrm{X}}{\to }}$ Lignite $\underset{\mathrm{Y}}{\overset{\mathrm{X}}{\to }}$ Bituminous coal $\underset{\mathrm{Y}}{\overset{\mathrm{X}}{\to }}$ Anthracite

$\mathrm{X}$ and $\mathrm{Y}$ refers to:

The image shows petroleum and natural gas deposits.

Why is the layer of oil formed between natural gas and water?

The byproducts of petroleum obtained after processing it, used as fuel are:

(i) Diesel and kerosene  (ii) Paraffin wax and fuel  (iii) Petrol and CNG  (iv) LPG and fuel oil