According to paragraph 3, the presence of the tsetse fly in eastern and central Africa caused which of the following A. People in the sub-Saharan region began to focus more on the cultivation of cereal crops than in maintaining livestock. B. Raids among neighboring cattle herders increased dramatically. C. Cattle herders spread south where they could graze their stock in tsetse-fly-free areas. D. Most hunter-gatherer groups limited their food collection to the tsetse-fly-free areas south of the Sahara.