Concept:Indirect rule in Northern Nigeria was adopted primarily to further Britain's economic interests through the existing traditional political system.Explanation:The British aimed at uninterrupted access to raw materials and markets for their industries.By ruling through the local emirs and chiefs, they maintained order with fewer officials and reduced resistance.This arrangement gave them firm control over trade and the collection of resources in the region.It was not intended to weaken the elite class, assist missionaries, or focus specifically on cheap labour for railway construction.Answer:A. ensure perfect control of the economy