Answers to Exercise 4：

　　1 to see　2 learning　3 having　4 to experiment　5 trying out　6 to find out　7 to develop

　　8 to fail　9 owning　10 sending

　　USING LANGUAGE

　　Reading

　　Suggested answers to Exercise 1：

　　1 They are a great way to stop crop disease and increase production.

　　2 They can damage the land by killing helpful bacteria and pests and by staying in the ground and underground water for a long time.They damage people's health by building up in their bodies and leading to cancer or other illnesses.

　　3 Organic farming means growing crops without using any chemicals.

　　4 The main reason for using organic farming methods is to grow good food and to avoid damaging the environment or people's health.

　　Suggested answers to Exercise 2：

Methods of organic farming Advantages of methods 1 Farmers use natural waste from animals.

2 Farmers often change the kind of crop in each field every few years.

3 Farmers plant crops with different lengths of roots.

4 Farmers sometimes plant grass between crops and leave it in the ground. 1 This makes the soil richer in minerals and so more fertile.

2 Changing the crops renews the minerals in the soil and helps it become rich and healthy.

3 This uses different levels of soil.

4 This prevents wind or water from carrying away soil and acts as a natural fertilizer. 　　Suggested answers to Exercise 3：

　　Step 1：main idea

　　Chemical fertilizers can cause many problems，so organic farming is becoming more popular.

　　Step 2：underlining and rewording topic sentences

　　Paragraph 1：Recently，however，scientists have been finding that long­term use of these fertilizers can cause damage to the land and，even more dangerous，to people's health.→In recent days，scientists have discovered that using chemical fertilizers for a long time can hurt the land and also people's health.

　　Paragraph 2：What are some of the problems caused by chemical fertilizers？→There are several problems caused by chemical fertilizers.

　　Paragraph 3：With these discoveries，some farmers and many customers are beginning to turn to organic farming.→Organic farming is becoming more popular with some farmers and many customers after these discoveries came out.

Paragraph 4：Organic farmers also use many other methods to keep the soil fertile.→There are