Concept:The Nupe Kingdom achieved its greatest power under a specific 19th-century ruler known for military and administrative reforms.Explanation:Etsu Mamudu was the king who led the Nupe Kingdom to its peak.He ruled during the 19th century and worked to strengthen the army and government.His policies helped expand Nupe territory and increase its influence across the region.This made the Nupe a dominant and prosperous kingdom during his reign.Answer:B. Etsu Mamudu