Concept:Densely populated areas are those with favourable conditions for human settlement and economic activities.
Explanation:South-western Nigeria contains major urban and commercial centres such as Lagos and Ibadan.
These centres attract large numbers of people because of employment, trade, and industry.
The region also has fertile soil and a relatively favourable climate for farming.
Because of these opportunities, south-western Nigeria is one of the most densely populated areas in Tropical Africa.
The middle belt, the Sahel region, and the Niger Delta are less densely populated when compared with south-western Nigeria.
Answer:A. South-western Nigeria