Concept:Pan-Africanism was an external ideological movement that encouraged African unity and freedom from colonial rule.
Explanation:Pan-Africanism inspired black people all over the world to struggle for their rights.
It gave Nigerian nationalists a strong sense of pride and purpose.
Through Pan-African meetings and ideas, nationalists learnt how to demand political independence clearly.
The movement provided moral support for the fight against colonial rule in Nigeria.
It also connected Nigerian struggles to the wider African and black liberation movements.
Thus, it was the major external factor that promoted nationalism in Nigeria.
Answer:A. Pan-Africanism