Final answer:
The most centralized 14th-century Bantu kingdom that wasn't in West Africa was Zimbabwe. Therefore, the correct option is b).
Step-by-step explanation:
The most tightly centralized of the 14th-century Bantu kingdoms was Zimbabwe. The other options, Ghana, Kongo, and Mali, are all located in West Africa, whereas Great Zimbabwe was located in the southern part of Africa, making it part of a different cultural and political milieu. When discussing the empires of West Africa, notable examples include the Ghana Empire, the Mali Empire, notable for influential rulers like Sundiata Keita and Mansa Musa, and the Songhai Empire, which rose to prominence later. However, Great Zimbabwe is distinct as it was part of the Shona civilization on the Zimbabwean plateau, known for its large stone structures and trading prowess in the central South African interior.
Therefore, the correct option is b).