Answer: According to the graph provided, at least half of people practice Christianity only in (C.) Zimbabwe and South Africa.
Explanation: The graph provided shows that 50% of the people living in Zimbabwe practice Christianity. Moreover, it also indicates that 83% of the people living in South Africa, that is to say the great majority, practice Christianity. Therefore, in Zimbabwe half of the population is Christian, while in South Africa more than half of the population is Christian. In contrast, less than half of the population in Nigeria practice Christianity (only 40%). Furthermore, very few people practice Christianity in Mali (only 1%).