Concept:The amalgamation of Nigeria's protectorates was a colonial administrative merger carried out under British rule.Explanation:Lord Frederick Lugard served as the Governor-General of Nigeria.He officially merged the Northern and Southern protectorates into a single territory.This unification took effect on the 1st of January, 1914.The date marked the beginning of a unified Nigerian administration under British control.Answer:D. 1 January, 1914