15000 bài tập tách từ đề thi thử môn Tiếng Anh có đáp án (Phần 63)

In the world to day, particularly in the two most “industrialized areas, North America and Europe, recyling is big news. People are talking about it, practicing it, and discovering new ways to be sensitive to the environment. Recycling means finding was to use products a second time. The motto of the recycling movement is “Reduce, Reuse, Recycle”.

This first step is to reduce garbage. In stores, a shopper has to buy products in blister packs, boxes and expensive plastic wrappings. A hamburger form a fast food restaurant comes in lots of packaging: usually paper, a box, a bag. All that packaging is wasted resources. People should try to buy things that are wrapped simply, and to reuse cups and utensils. Another way to reduce waste is to buy high-quality products. When low quality appliances break, many customers throw them away and buy new ones – a loss of more resources and more energy. For example, if a customer buys a high-quality appliance that can be easily repaired, the manufacturer receives an important message. In the same way, if a customer chooses a product with less packaging, that customer sends an important message to the manufacturers. To reduce garbage, the throwaway must stop.

The second step is to reuse. It is better to buy juices and soft drinks in returnable bottles. After customers empty the bottles, they return them to the store. The manufacturers of the drinks collect the bottles, wash them, and then fill them again. The energy that is necessary to make new bottles is saved. In some parts of the word, returning bottles for money is a common practice. In those places, the garbage dumps have relatively little glass and plastic from throwaway bottles.

The third step is being environmentally sensitive is to recycle. Spent motor oil can be cleaned and used again. Aluminum cans are expensive to make. It takes the same amount of energy to make one aluminum can as it does to run a color TV set for three hours. When people collect and recycle aluminum (for new cans), they help save one of the world’s precious resources.

Telecommuting is some form of computer communication between employees’homes and offices. For employees whose job involve sitting at a terminal or word processor entering data or typing reports, the location of the computer is of no consequence. If the machine can communicate over telephone lines, when the work is completed, employees can dial the office computer and transmit the material to theiremployer. A recent survey in USA Today estimates that there are approximately 8,7 million telecommuters. But although the numbers are rising annually, the trend does not appear to be as significant as predicted when Business Week published “ The Portable Executive” as its cover story a few years ago. Why hasn’t telecommuting become more popular?

    Clearly, change simply takes time. But in addition, there has been active resistance on the part of many managers. These executives claim that supervising the telecommuters in a large work force scattered across the country would be too difficult, or, at least, systems for managing them are not yet developed, thereby complicating the manager’s responsibilities.

    It is also true that employees who are given the option of telecommuting are reluctant to accept the opportunity. Most people feel that they need regular interaction with a group, and many are concerned that they will not have the same consideration for advancement if they are not more visible in the office setting. Some people feel that even when a space in their homes is set aside as a work area, they never really get away from the office.

In addition to providing energy, fats have several other functions in the body. The fat soluble vitamins, A, D, E, and K, are dissolved in fats, as their name implies. Good sources of these vitamins have high oil or fat content, and the vitamins are stored in the body’s fatty tissues. In the diet, fats cause food to remain longer in the stomach, this increasing the feeling of fullness for some time after a meal is eaten. Fats add variety, taste and texture to foods, which accounts for the popularity of fried foods. Fatty deposits in the body have an insulating and protective value. The curves of the human female body are due mostly to strategically located fat deposits.

Whether a certain amount of fat in the diet is essential to human health is not definitely known. When rats are fed a fat-free diet, their growth eventually ceases, their skin becomes inflamed and scaly, and their reproductive systems are damaged. Two fatty acids, linoleic and acids, prevent these abnormalities and hence are called essential fatty acids. They also are required by a number of other animals but their roles in human beings are debatable. Most nutritionists consider linoleic fatty acid an essential nutrient for humans.

An air pollutant is defined as a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetation, or materials adversely. Air pollution requires a very flexible definition that permits continuous change. When the first air pollution laws were established in England in the fourteenth century, air pollutants were limited to compounds that could be seen or smelled - a far cry from the extensive list of harmful substances known today. As technology has developed and knowledge of the health aspects of various chemicals has increased, the list of air pollutants has lengthened. In the future, even water vapor might be considered an air pollutant under certain conditions.

Many of the more important air pollutants, such as sulfur oxides, carbon monoxide, and nitrogen oxides, are found in nature. As the Earth developed, the concentration of these pollutants was altered by various chemical reactions; they became components in biogeochemical cycles. These serve as an air purification scheme by allowing the compounds to move from the air to the water or soil. On a global basis, nature's output of these compounds dwarfs that resulting from human activities.

However, human production usually occurs in a localized area, such as a city. In such a region, human output may be dominant and may temporarily overload the natural purification scheme of the cycles. The result is an increased concentration of noxious chemicals in the air. The concentrations at which the adverse effects appear will be greater than the concentrations that the pollutants would have in the absence of human activities. The actual concentration need not be large for a substance to be a pollutant; in fact, the numerical value tells us little until we know how much of an increase this represents over the concentration that would occur naturally in the area. For example, sulfur dioxide has detectable health effects at 0.08 parts per million (ppm), which is about 400 times its natural level. Carbon monoxide, however, has a natural level of 0.1 ppm and is not usually a pollutant until its level reaches about 15 ppm.