Why are coal and petroleum categorised as natural resources? Give a reason as to why they should be used judiciously.

Coal and petroleum are categorised as natural resources because they are formed naturally from the remains of dead plants and animals (biomass) buried deep under the earth under high pressure and temperature over millions of years, without any human intervention.

They should be used judiciously because:

1. Exhaustibility: They are non-renewable resources. Their reserves are limited, and since they take millions of years to form, they will get exhausted rapidly if consumed at the current high rate.
2. Environmental Pollution: Burning coal and petroleum releases harmful gases like carbon dioxide ($CO_2$), sulfur dioxide ($SO_2$), and nitrogen oxides ($NO_x$). These gases cause air pollution, acid rain, and enhance the greenhouse effect, leading to global warming.