Concept:The reform created a system in which the traditional ruler governs with a council of advisers.Explanation:The old system gave one traditional ruler sole authority as a Native Authority.In 1952, the Northern Region abolished this sole Native Authority system.It was replaced with the Chief-in-Council arrangement.Under this system, the traditional ruler acts with and on the advice of a council.Therefore, traditional rulers became Chief-in-Council.Answer:D. Chief-in-Council