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必修4《Using LanguageⅠ》最新PPT课件优质课下载
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Fertilizers?
Chemical fertilizers
Natural fertilizers
____________ farming
____________ farming
chemical
organic
Chemical or Organic Farming?
Predict what we will know from the passage.
— We'll know...
Chemical or Organic Farming?
Task 1 Underline the topic sentence of each paragraph.
A
What are some of the problems caused by chemical fertilizers? First, they damage the land by 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, therefore, animals and humans, since chemicals get inside the crops and cannot just be washed off. These chemicals in the food supply build up in people’s bodies over time. Many of these chemicals can lead to cancer or other illnesses. In addition, fruit, vegetables and other food grown with chemical fertilizers usually grow too fast to be full of much nutrition. They may look beautiful, but inside there is usually more water than vitamins and minerals.
Task 1 Underline the topic sentence of each paragraph.
A. What are some of the problems caused by chemical fertilizers?
B. ...____________________________________________________
C. ...____________________________________________________
D. ...____________________________________________________
Task 1 Underline the topic sentence of each paragraph.
B
With these discoveries, some farmers and many customers are beginning to turn to organic farming. Organic farming is simply farming without using any chemicals. They focus on 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 from animals as fertilizer. They feel that this makes the soil in their fields richer in minerals and so more fertile. This also keeps the air, soil, water and crops free from chemicals.
Task 1 Underline the topic sentence of each paragraph.
C