根据课文填空，每空一词。 What are some of the problems caused by chemical fertilizers? First, they damage the land l_____ killing the helpful bacteria and pests as well as the harmful ones. Chemicals also stay in the ground and underground water for a long time. This affects crops and, 2_____, animals and humans, 3_____ chemicals get inside the crops and cannot just be washed 4_____. These chemicals in the food supply build 5_____ in people's bodies over time. Many of these chemicals can lead 6_____ cancer or other illnesses. 7_____ addition, fruit, vegetables and other food grown with chemical fertilizers usually grow 8_____ fast to be full of much nutrition. They may look beautiful, 9_____ inside there is usually more water than vitamins and minerals. 10_____ these discoveries, some farmers and many customers are beginnng to tum to organic farming. Organic farming is simply farming 11_____ using any chemicals. They focus 12_____ keeping their soil rich and free of disease. A healthy soil reduces disease and helps crops grow strong and healthy. Organic farmers, therefore, often prefer using natural waste 13_____ animals as fertilizer. They feel that this makes the soil in their fields 14_____ in minerals and so more fertile. This also keeps the air, soil, water and crops 15_____ from chemicals.