Concept:Colonial mining in Nigeria was an instrument of imperial exploitation.Explanation:The colonial government encouraged mining so that Nigerian mineral resources like tin and coal could be extracted and exported mainly for Britain’s benefit.It was not meant to build a balanced Nigerian economy or make Nigeria self-reliant.The railway was simply a tool for transporting the minerals, not the main purpose of the mining industry.Therefore, the mining industry was promoted to maximise the exploitation of Nigeria’s resources.Answer:D. maximize exploitation.