根据以下资料，回答题： Centuries -考呗网题库移动版

单选题根据以下资料，回答题：
        Centuries ago, man discovered that removing moisture from food helps to preserve it, and that the easiest way to do this is to expose the food to sun and wind．In this way the North American Indians produce pemmican (dried meat ground into powder and made into cakes), the Scandinavians make stockfish and the Arabs dried dates and "apricot leather"．
        All foods include water---cabbage and other leaf vegetables contain as much as 93% water, potatoes and other root vegetables 80%, lean meat 75% and fish, anything from 80% to 60%, depending on how fatty it is．If this water is removed, the activity of the bacteria which cause food to go bad is checked． Fruit is sun-dried in Asia Minor, Greece, Spain and other Mediterranean countries, and also in Califomia, South Africa and Australia．The methods used vary, but in general, the fruit is spread out on trays in drying yards in the hot sun．In order to prevent darkening, pears, peaches and apricots are exposed to the fumes of burning sulfur before drying．Plums, for making prunes, and certain varieties of grapes for making raisins and currants, are dipped in an alkaline solution         in order to crack the skins of the fruit slightly and remove their wax coating, so as to increase the rate of drying．
Nowadays most foods are dried mechanically．The conventional method of such dehydration is to put food in chambers through which hot air is blown at temperatures of about 110~C at entry to about 43°C at exit．This is the usual method for drying such things as vegetables, minced meat, and fish．
        Liquids such as milk, coffee, tea, soups and eggs may be dried by pouring them over a heated steel cylinder by spraying them into a chamber through which a current of hot air passes．In the first case, the dried material is scraped off the roller as a thin film which is then broken up into small, though still relatively coarse flakes．In the second process it falls to the bottom of the chamber as a fine powder．Where recognizable pieces of meat and vegetables are required, as in soup, the ingredients are dried separately and then mixed．
        Dried foods take up less room and weigh less than the same food packed in cans or frozen, and they do not need to be stored in special conditions．For these reasons they are invaluable to the climbers, explorers and soldiers in battle, who have little storage space．They are also popular with housewives because it takes so little time to cook them．Usually it is just a case of replacing the driedout moisture with boiling water．

The open-air method of drying food

A．is the one most commonly used today
B．was invented by the American Indians
C．has been known for hundreds of years
D．tends to be unhygienic

参考答案C

解析:第一段提到，人们在数世纪之前就发现给食物脱水有助于食物保存。
第二段指出所有的食物都含水，如果将水除去，就可以抑制导致食物变质的细菌的活动。
第三段简要介绍了世界各地制作果干以及使果干不变颜色的方法。
第四段指出现在许多食物都是靠机械方式脱水的。
第五段主要介绍了液体的干燥方法。
最后一段总结了脱水食物的优点：占空间小、重量轻、无需特殊储存条件、便于烹饪等等。
C。本题出题点在文章开头处。根据题干信息将答案锁定在文章首句。文章开头提到，数世纪之前，人们就发现将食物中的水去除有助于保存食物，而给食物脱水最简单的方法是将食物暴露于阳光和风之中，由此推断，人们熟悉露天风干食物的方法已经有几百年了，故选C。

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A．cannot live in sunlight
B．are killed by drying
C．are in no way dependent on the water content
D．have their activity greatly reduced by drying

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单选题 Alkaline solutions are used to

A．prevent darkening of certainfruit
B．crack the skins of certain fruit
C．produce special wax coating
D．decrease the rate of drying

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单选题 Nowadays vegetables are most commonly dried

A．on horizontal cylinders
B．in hot-air chambers
C．in the sun and wind
D．by using the open tray method

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