Concept:The decline of the Oyo Empire created a power vacuum that allowed other Yoruba states to rise.Explanation:After the fall of Oyo in the 19th century, Ibadan emerged as a strong military and political power.It expanded rapidly and became the most prominent successor state among the Yoruba.Other states like Egba, Ife, and Ijebu did not gain the same level of regional dominance.Answer:Ibadan.