The correct answer is (c) Nigeria.
Nigeria is the most populous country in Africa, with a population of over 200 million people. It is a federal republic consisting of 36 states and the Federal Capital Territory. The capital city is Abuja.
Egypt is the second most populous country in Africa, with a population of over 100 million people. It is a republic with a presidential system of government. The capital city is Cairo.
Ethiopia is the third most populous country in Africa, with a population of over 100 million people. It is a federal republic consisting of 9 states and 2 city administrations. The capital city is Addis Ababa.
South Africa is the fourth most populous country in Africa, with a population of over 50 million people. It is a constitutional republic consisting of 9 provinces. The capital city is Pretoria.