15000 bài tập tách từ đề thi thử môn Tiếng Anh có đáp án (Phần 7)

The attraction of gold is as old as history. Since ancient times, gold has been the object of dreams and obsessions. Western literature is full of characters who kill for gold or hoard it, from King Midas in the ancient Greek myths, to Fagin in Dickens' Oliver Twist. These characters go to evil extremes to get or keep their gold and they get the punishment they deserve. Most people would not be willing to go to such extremes, of course, but they would not question the assumption that gold has lasting value above and beyond any local currency. Societies change over time, customs and currencies evolve, but gold remains. A wedding ring, for example, must be gold, and so should any serious gift of jewelry. In fact, giving and wearing gold is still a mark of prestige in our post-industrial society, though gold is no longer valued as it used to be thousands of years ago.

Why is gold so valuable? True, it is shiny, durable, and rare, but it is far less useful than many other minerals or metals. It is also not like stock in a company, where the value of the stock depends on the performance of the company. Gold, on the contrary, like any currency, is valuable precisely because people believe it is valuable. That is, if people were willing to accept seashells for their labor and could use them to pay for food, fuel, and other commodities, then seashells would become a valuable currency. Thus, the value of gold depends on the collective belief that gold will continue to be valuable. As long as demand for gold remains steady, the price will hold steady; if demand is high, it will continue to increase in value. But if people should someday lose faith in gold, the price of gold could fall sharply.

Another factor that has affected the price of gold has been the increasing difficulty in acquiring it. Today, most of the gold left in the grounds is in microscopic pieces mixed with rock. To get it, miners must dig up tons and tons of rock, and then spray it with chemicals to separate out the gold. For one ounce of gold - a wedding ring, for example - the mine processes about 30 tons of rock. This is already a costly operation. But there are also hidden social and environmental costs. The mining and processing of gold is ruinous to the environment and to the health of people living nearby. Most of these mines are in poor regions where the people have had little voice in whether there should be mines and how the mines should be run. The large multinational mining companies simply bought the land and opened the mines. However, as people and governments begin to realize the extent of the damage caused by the mines, the situation might change. Indeed, if the mining companies ever have to pay the full environmental and social costs of mining gold, the price of gold is likely to climb yet higher.

Bees, classified into over 10,000 species, are insects found in almost every part of the world except the northernmost and southernmost regions. One commonly known species is the honeybee, the only bee that produces honey and wax. Humans use the wax in making candles, lipsticks, and other products, and they use the honey as a substance that people eat to maintain life and growth. While gathering the nectar and pollen with which they make honey, bees are simultaneously helping to fertilize the flowers on which they land. Many fruits and vegetables would not survive if bees did not carry the pollen from blossom to blossom.

Bees live in a structured environment and social structure within a hive, which is a nest with storage space for the honey. The different types of bees each perform a unique function. The worker bee carries nectar to hive in a special stomach called a honey stomach. Other workers make beeswax and shape it into a honeycomb, which is a waterproof mass of six-sided compartments, or cells. The queen lays eggs in completed cells. As the workers build more cells, the queen lays more eggs.

All workers, like the queen, are female, but the workers are smaller than the queen. The male honeybees are called drones; they do no work and cannot sting. They are developed from unfertilized eggs, and their only job is to impregnate a queen. The queen must be fertilized in order to lay more worker eggs. During the season when less honey is available and the drone is of no further use, the workers block the drones from eating the honey so that they will starve to death.

Before the 1500’s, the Western plains of North America were dominated by farmers. One group, the Mandans, lived in the upper Missouri River country, primarily in present-day North Dakota. They had large villages of houses built close together. The tight arrangement enabled the Mandans to protect themselves more easily from the attacks of others who might seek to obtain some of the food these highly capable farmers stored from one year to the next.

The women had primary responsibility for the fields. They had to exercise considerable skill to produce the desired results, for their northern location meant fleeting growing seasons. Winter often lingered; autumn could be ushered in by severe frost. During the spring and summer, drought, heat, hail, grasshoppers, and other frustrations might await the wary grower.

Under such conditions, Mandan women had to grow maize capable of weathering adversity. They began as early as it appeared feasible to do so in the spring, clearing the land, using fire to clear stubble from the fields and then planting. From this point until the first green corn could be harvested, the crop required labor and vigilance. Harvesting proceeded in two stages. In August the Mandans picked a smaller amount of the crop before it had matured fully. This green corn was boiled, dried, and shelled, with some of the maize slated for immediate consumption and the rest stored in animal-skin bags. Later in the fall, the people picked the rest of the corn. They saved the best of the harvest for seeds or for trade, with the remainder eaten right away or stored for later use in underground reserves. With appropriate banking of the extra food, the Mandans protected themselves against the disaster of crop failure and accompanying hunger.

The women planted another staple, squash, about the first of June, and harvested it near the time of the green corn harvest. After they picked it, they sliced it, dried it, and strung the slices before they stored them. Once again, they saved the seed from the best of the year`s crop. The Mandans also grew sunflowers and tobacco; the latter was the particular task of the older men.