Increasingly, over the past ten years, people-especially young people have become aware of the need to change their eating habits, 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 foods: foods which do not contain chemical additives and which have not been affected by chemical fertilizers（化肥）widely used in farming today.

    Natural foods, for example, are vegetables, fruit and grain 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 foods grown in commercial farming areas.

    Natural foods also include animals which have been allowed to feed and move freely in healthy pastures（生活状况）. Compare this with what happens in the mass production of poultry（家禽）: there are battery farms, for example, where thousands of chickens live crowded together in one building and are fed on food which is little than rubbish. Chickens kept in this way are not only tasteless as food; they also produce eggs which lack important vitamins.

    There are other aspects of healthy eating which are now receiving increasing attention from experts in diet. Take, for example, the question of sugar. This is actually a nonessential food! It is not that sugar is harmful in itself. But it does seem to be additive: the quantity we use has grown steadily and in Britain today each person consumes an average of 200 pounds a year! Yet all it does is provide us with energy, in the form of calories. There are no vitamins in it, no minerals and no fibre.

工业上可利用黄铁矿（主要成分是Fe₂S）煅烧的产物冶炼铁和生产硫酸，其反应方程如下：

①4FeS₂+11O₂2Fe₂O₃+8SO₂②Fe₂O₃+3CO2Fe+3CO₂③2SO₂+O₂2SO₃④SO₃+H₂O═H₂SO₄

下列说法不正确的是（　　）

师生交往中，我们偶尔会被老师误解，也会与老师发生矛盾。对此，正确的处理方法是（    ）