Why Are Large Areas of East Africa Devoid of Cattle

Why are large areas of East Africa devoid of cattle today?

A) because changes introduced by European intruders allowed the multiplication and uncontrolled spread of the tsetse fly, which carries illnesses that are fatal to both humans and livestock
B) because the natives of the region practiced a scorched earth policy of defense against European intruders in which they slaughtered their own herds and burned down their own villages
C) because European intruders forced economic changes on the native peoples including the transformation from activities based on nomadic cattle herding and grazing to activities based on sedentary grain farms and enclosed private estates
D) because European cattle farmers resented the cheap imports that flowed into the continent after colonization and colonial administrators were pressured to destroy millions of animals owned by natives
E) because the African cattle transmitted diseases to Europeans that the native peoples had resistance to and the subsequent substitution of European cattle breeds for the African breeds proved unsuccessful