Although africa is a large, diverse area, it has little fertile soil. drought, disease, and insects threaten africa's crops. what must africans do to capitalize on their land as a resource? a) they must concentrate on diamond trade instead of farming. b) they must develop irrigation techniques and disease-resistant crops. c) they must develop trade areas inorder to learn to survive rough conditions. d) they must mine for gold and accept the fact that their land cannot be farmed.