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.