What country in saharan and southern africa has the highest population?

A. South Africa

B. Nigeria

C. Angola

D. Congo

South Africa = around 55,000,000 of total population (based on 2015 data)

Nigeria = around 185,000,000 of total population (2015 data)

Angola = around 25,000,000 of total population (2014 data)

Congo = around 82,000,000 of total population (2015 data)

Given that there's not an high population growth or birth rate or something like that, I'd say Nigeria