[单项选择] Many Americans harbour a grossly distorted and exaggerated view of most of the risks surrounding food. Fergus Clydesdale, head of the department of food science and nutrition at the University of Massachusetts-Amherst, says bluntly that if the dangers from bacterially contaminated chicken were as great as some people believe, "the streets would be littered with people lying here and there." Though the public increasingly demands no-risk food, there is no such thing. Bruce Ames, chairman of the biochemistry department at the University of California, Berkeley, points out that up to 10% of a plant’’s weight is made up of natural pesticides (杀虫剂). Says he :"Since plants do not have jaws or teeth to protect themselves, they employ chemical warfare." And many naturally produced chemicals, though occurring in tiny amounts, prove in laboratory tests to be strong carcinogens--a substance which can cause cancer. Mushrooms (磨菇) might be banned if they were judged by the same standards t
A. plants produce certain chemicals to combat pests and diseases.
B. plants absorb useful chemicals to promote their growth.
C. farmers use man-made chemicals to dissolve the natural chemicals in plants.
D. farmers use chemicals to protect plants against pests and diseases.