The correct answer is Mauritius.
Mauritius is an island nation in the Indian Ocean, east of Madagascar. It has a population of 1.29 million people and a land area of 2,040 square kilometers. This gives it a population density of 634 people per square kilometer.
Rwanda is a landlocked country in East Africa. It has a population of 12.6 million people and a land area of 26,338 square kilometers. This gives it a population density of 480 people per square kilometer.
Burundi is a landlocked country in Central Africa. It has a population of 11.7 million people and a land area of 27,834 square kilometers. This gives it a population density of 420 people per square kilometer.
Sierra Leone is a country in West Africa. It has a population of 7.8 million people and a land area of 71,740 square kilometers. This gives it a population density of 109 people per square kilometer.
Mauritius is the most densely populated country in Africa because it has a relatively small land area and a large population. The other three countries are all landlocked and have larger land areas, which means that they have lower population densities.