Geographical reasons for the following are : (i) Port cities have their own oil refineries because two thirds of the petroleum is imported. The crude oil is imported from Gulf countries and Malaysia. (ii) Petroleum is called fossil fuel because it is derived from plant and animal . life buried in sedimentary rocks millions of years ago. (iii) Coal is called a versatile mineral because it forms a basic raw material for the production of chemicals, dyes, fertilizers, paints, synthetics, explosive apart from source of energy.