Answer: D. Teach the public energy conservation
Coal is an efficient and inexpensive source of energy which provides a stable and large scale energy generation in the form of electrical and thermal energy. It is a type of fossil fuel which is most abundantly present. But it is also a non- renewable source of energy, and cannot be replenished after a single use. It is used as a source of generation of electricity, production of metallic objects, manufacturing of a liquid fuel, engines of local trains and for other purposes. As, it is a non- renewable resource it should be used in a sustainable way.
Hence, D. Teach the public energy conservation is the correct option.