A、The change of eating habits. B、Healthy diet. C、Natural food. D、Processed food. C题目问的是下面哪个是文章的最佳标题。综合全文可知，整篇文章的重点都是在讲自然食品。故选C。

Increasingly, over the past ten years, people—especially young people—have become aware of the need to change their eating habits. That is because much of the food they eat, particularly processed food, is not good for the health. Consequently, there has been a growing interest in natural food: which does not contain chemical additives and which have not been affected by chemical fertilizers widely used in farming today. Natural food, for example, is vegetables, fruits and grains which have been grown in soil that is rich in organic matter. In simple terms, this means that the soil has been nourished by unused vegetable matter, which provides it with essential vitamins and minerals. This in itself is a natural process compared with the use of chemicals and fertilizers, the main purpose of which is to increase the amount—but not the quality—of food grown in commercial farming areas.
    Q28: Which of the following is the best title for this passage?
    Q29: Why have people become more interested in natural food?
    Q30: What is the farmers’ purpose to use chemicals and fertilizers?