题干

我们知道,植物主要通过根毛吸收土壤中的水分,如果一次施肥过多,根毛细胞不但吸收不到水分,反而要失去水分,从而使植物萎蔫,即“烧苗”.该现象说明(  )

A:植物的生活需要水,不需要无机盐

B:植物吸收水分与土壤中无机盐浓度有关

C:无机盐只有溶解在水中才能被吸收

D:植物生活对水和无机盐的需求量不同

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答案(点此获取答案解析)

B

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阅读理解

    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.