[单项选择]

Biotechnologists have developed genetically modified rice that is fortified with beta-carotene which the body converts into vitamin A and additional iron, and they are working on three kinds of nutritionally improved crops. Biotech can also improve farming productivity in places where food shortages are caused by crop damage attributable to pests, drought, poor soil and crop viruses, bacteria or fungi. Damage caused by pests is incredible. In trials of pest-resistant cotton in Africa yields have increased significantly. So far, fears that genetically modified, pest-resistant crops might kill good insects as well as bad appear unfounded. Viruses often cause massive failure in staple crops in developing countries. Two years ago Africa lost more than half its cassava crop — a key source of calories — to the mosaic virus. Genetically modified, virus-resistant crops can reduce that damage, as can drought-tolerant seeds in regions where water shortage limits the amount of l
A. sole solution
B. the whole answer
C. useless
D. reality