Concept:The transformation of the OAU into the AU was championed by a specific African head of state.Explanation:Thabo Mbeki of South Africa spearheaded the transformation.He promoted the idea of replacing the OAU with a stronger continental union.The African Union was formally launched in 2002 in Durban, South Africa.Mbeki’s diplomatic leadership was central to achieving this change.The other leaders listed did not play that leading role.Answer:A. Thabo Mbeki