The correct answer is option c) The most densely populated in Africa.
Most Africans maintain a rural lifestyle, but urbanization increases as people leave the countryside to look for work in the cities. The highest population densities are found where water is more accessible, such as in the Nile Valley, the north and west coasts, and along the Niger River.
Options A) and B) are relevant to the topic sentence, however, they are only supporting statements.
Option D) is incorrect