题目内容
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The use of chemicals and fertilizers in farming is meant to increase ______.
A．the quantity of foods
B．the quality of foods
C．either the quantity or the quality of foods
D．the quality as well as the quantity
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According to the author, the use of chemicals and fertilizers______.
A．will not necessarily increase the production of foods
B．is a good way to improve the quality of foods
C．promotes the foods both in quality and in quantity
D．is no good for health
A.do experiments with water
B.purify the used water and reuse it
C.use fresh water once again
D.make use of seawater
This mass of metals, paper, food, plastic, rubber and glass which is all mixed together seems of no earthly use to anyone.
Or is it？ Scattered efforts across the country indicate that new technology, properly applied, might someday turn these millions of tons of refuse into an excellent source of raw materials for new uses.
Several new projects are carried out to study the possibility of treating wastes through pyrolysis (高温分解)--a system of reducing refuse to basic chemicals, liquids and gases which have commercial value. In Florida, a special tube system provides automatic transport of refuse to a central collection building.
In short, many new ideas are being tested, and many will be needed, since no one method is likely to prove suitable everywhere.
However, many difficult economic and social questions must be answered before real progress can be made. Can recovered materials compete with new materials？ What will be needed as encouragement to make resource recovery work？ Will citizens pay the costs of changing our waste system？
The article suggests that garbage and refuse from homes and public places ______.
A．make up the largest percentage of solid wastes
B．make up a small percentage of solid wastes
C．are not really considered in the solid waste problem
D．are considered of no use to the earth
For example, it is recorded in many history books the people who lived over three thousand years ago ate salted fish. Thousands of years ago in Egypt, salt was used to preserve the dead.
In some periods of history, a person who stole salt was thought to have broken the law. Take the eighteenth century for an example, if a person was caught stealing salt, he would be thrown into prison. History also records that only in England about ten thousand people were put into prison during that century for stealing salt! About one hundred and fifty years ago, in the year 1553, if a man took more than his share of salt, he would be thought to have broken the law and would be seriously punished. The offender' s ear was cut off.
Salt was an important item on the dinner table of a king. It was always placed in front of the king when he sat down to eat. Important guests at the king' s table were seated near the salt. Less important guests were given seats farther away from it.
Thousands of years ago in Egypt, salt was used ______.
A．to punish people who had broken the law
B．to keep dead bodies from decay
C．to keep fish alive
D．to make chemicals
The Chinese have used a method called acupuncture(针炙) to perform. operations for about 4,000 years without putting the patient to sleep. This involves placing flexible needles into certain parts of the body. The needles are available in a number of stores in China and anyone may buy them.
To learn how to use the needles takes about one month of training. But to be skillful requires greater time. (79) The person who performs the acupuncture knows how to put in the needles so the needles themselves are not painful. This person also knows where to place the needles so the patient feels no pain in the area where the operation is to be performed. A particular operation might require 25 or more needles placed in various parts of the body. But now this operation requires only 3 or 4 needles.
Today, the Chinese doctors are trying to learn more about acupuncture. (80) They are trying to develop a convincing theory to explain how the needles work in preventing pain, or why a needle in the wrist, for example, Would prevent the pain in the area of the mouth.
A patient who needs an operation is given a choice between having acupuncture or having one of the chemicals used for putting him to sleep. It has been estimated that over half of the patients choose acupuncture because there is no sickness after the operation but the chemical may make the patient sick for a few hours or a day.
Acupuncture is ______.
A．a medical operation
B．a medical needle
C．a medical technique
D．a medical machine
For example, it is recorded in many history books that people who lived over 3000 years ago ate salted fish. Thousands of years ago in Egypt, salt was used to preserve the dead.
In some periods of history, a person who stole salt was thought to have broken the law. Take the eighteenth century for example, if a person was caught stealing salt, he would be thrown into prison. History also records that only in England about ten thousand people were put into prison during that century for stealing salt! About 450 years ago, in the year 1553, if a man took more than his share of salt, he would be thought to have broken the law and would be seriously punished. The offender's ear was cut off.
Salt was an important item on the dinner table of a king. It was always put in front of the king when he sat down to eat. Important guests at the king's table were seated near the salt. Less important guests were given seats farther away from it.
Thousands of years ago in Egypt salt was used ______.
A．to punish people who had broken the law
B．to keep dead bodies from decay
C．to keep fish alive
D．to make chemicals
Researchers have long known that stressing plants can force them to take defensive action, often ramping up the production of protective chemicals that, for example, make them more resistant to insect attack. It has become common practice to stress such plants into increasing their yields. This is usually clone using physical stress elicitors (诱导子), including bits of the micro-organisms that normally attack the plants, or irritants made from metallic compounds such as copper chloride. These are effective, but they come at a cost. Most elicitors are toxic to plants and can build up in tissues, making it necessary to occasionally "clean" a plant of the chemicals so they keep having the same effect.
Recently, research groups at the University of Arizona in Tucson found that the application of an electric current to the hairy roots of the poisonous herb Hyoscyamus muticus stimulated the production of the herb's toxin hyoscyamine (天仙子胺). This unpublished finding inspired Hans Van Etten, also of the University of Arizona, and his colleagues to test sub-lethal levels of electrical currents on other plants, to assess electricity's potential to elevate chemical production.
The researchers exposed eight different plant species (ranging from Japanese pagoda tree seedlings to pea plants) to weak electrical currents of 30 milliamps. Seven of the plants increased their production o{ defensive chemicals. The average boost of chemical production was 20 times, they report in Biotechnology Progress. One plant, a type of alfalfa, increased its chemical yield by 168 times. These values are very similar to those achieved using chemical elicitors, and seem to have no lethal effects-just a negative effect on growth. The treatment can be used over and over again without the build-up of any unwanted material.
The useful compounds would be very easy to harvest: they simply pour out into solution if the plants are grown hydroponically. "The fact that we can use electricity instead of toxic materials to elicit chemical production is very exciting because it means we get to look at how these chemicals form. without having to constantly add and remove toxins from the system," says Van Etten. "This is a really novel and creative approach that I've never seen before," says plant metabolic engineer Fabricio Medina Bolivar from Arkansas State University in Jonesboro. "The possibilities for using electricity with plants in this way are absolutely tremendous. "
Electricity acting on plants can be used to ______.
A．take precautions against skin infections
B．increase production of useful biologicals
C．increase pharmacological and commercial value
D．make plants more resistant to attack
Foods which do not contain chemical additives (添加剂) and which have not been affected by chemical fertilizers, 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 (有机的) 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(牧场). Compare this with what happens in the mass production of poultry: there are farms, for example, where thousands of chickens live crowded together in one building and are fed on food which is little better than rubbish. Chickens kept in this way are not only tasteless as food, they . also lay eggs which lack important vitamins.
There are other aspects of healthy eating which are now receiving increasing attention from experts on diet. Take, for example, the question of sugar. This is actually a non-essential food! Al though a natural alternative, such as honey, can be used to sweeten food if it is necessary, we can in fact do without it. It is not that sugar is harmful in itself. But it does seem to be addictive: the quantity we use has grown steadily over the last two centuries and in Britain today each person consumes an average of 200 pounds a year! Yet all it does is to provide us with energy, in the form. of calories. There are no vitamins in it, no minerals and no fiber.
It is significant that nowadays fiber is considered to be an important part of a healthy diet. In white bread, for example, the fiber has been removed．But it is present in unrefined flour and of course in vegetables. It is interesting to note that in countries where the national diet contains large quantities of unrefined flour and vegetables, certain diseases are comparatively rare. Hence the emphasis is placed on the eating of whole meal bread and more vegetables by modem experts on "healthy eating".
People have become more interested in natural foods because ________.
A．they are more health conscious
B．they want to taste all kinds of foods
C．natural foods are more delicious than processed foods
D．they want to return to nature
