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One billion people in the world are short of water. How can this problem be solved Some suggestions have been to desalinate ocean water or to build enormous water pipelines from areas where water is abundant. (Suggestions such as these prove extremely expensive when they are actually used. ) One possibility that scientists are considering is pulling icebergs from either the North Pole or the South Pole to parts of the world with a water shortage. Although many questions must be answered before such a project could be tried, moving icebergs seems a reasonable possibility in the future.Engineers, mathematicians, and glaciologists from a dozen countries have been considering the iceberg as a future source of water. Saudi Arabia is particularly interested in this project because it has a great water shortage. Scientists estimate that it would take 128 days to transport a large iceberg (about 1/2 square mile) to Saudi Arabia. Yet the iceberg would be completely melted by the 104th day. Therefore, insulation would be essential, but how to insulate the iceberg remains an unsolved problem.The problems in transporting an iceberg are numerous. The first problem is choosing the iceberg to pull. The icebergs that form in the North Pole are quite difficult to handle because of their shape. Only a small portion extends above the water — most of the iceberg is below the surface, which would make it difficult to pull. South Pole icebergs, on the other hand, are flat and float like table tops. Thus they would be much easier to move.How can a 200-million-ton iceberg be moved No ship is strong enough to pull such enormous weight through the water. Perhaps several ships could be used. Attaching ropes to an iceberg this size is also an enormous problem. Engineers think that large nails or long metal rods could be driven into the ice. What would happen if the iceberg splits into several pieces during the pulling Even if an iceberg with very few cracks were chosen, how could it be pulled through stormy waters Furthermore, once the iceberg reached its destination, very few ports would be deep enough to store it.All of these problems must be solved before icebergs can become a reasonable source of water. Yet scientists estimate that it will be possible to transport them in the near future. Each year, enough icebergs form to supply the whole world with fresh water for a full year. In addition, icebergs are free and nonpolluting. As a solution to the world’s water problems, icebergs may be a workable possibility. Why are icebergs from the South Pole probably easier to transport（）
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Scattered around the globe are more than 100 small regions of isolated volcanic activity known to geologists as hot spots. Unlike most of the world’s volcanoes, they are not always found at the boundaries of the great drifting plates that make up the earth’s surface. On the contrary, many of them lie deep in the interior of a plate. Most of the hot spots move only slowly, and in some cases the movement of the plates past them has left trails of dead volcanoes. The hot spots and their volcanic trails are milestones that mark the passage of the plates.That the plates are moving is now beyond dispute. Africa and South America, for example, are moving away from each other as new material is injected into the sea floor between them. The complementary coastlines and certain geological features that seem to span the ocean are reminders of where the two continents were once joined. The relative motion of the plates carrying these continents has been constructed in detail, but the motion of one plate with respect to another cannot readily be translated into motion with respect to the earth’s interior. It is not possible to determine whether both continents are moving in opposite directions or whether one ocean is stationary and the other is drifting away from it. Hot spots, anchored in the deeper layer of the earth, provide the measuring instruments needed to resolve the question. From an analysis of the hot-spot population it appears that it has not moved during the 30 million years.The significance of hot spots is not confined to their role as a frame of reference. It now appears that they also have an important influence on the geophysical processes that propel the plates across the globe. When a continental plate comes to rest over a hot spot, the material rising from deeper layers creates a broad dome. As the dome grows, it develops deep fissures (cracks); in at least a few cases the continent may break entirely along some of these fissures, so that the hot spot initiates the formation of new ocean. Thus just as earlier theories have explained the mobility of the continents, so hot spots may explain the mobility of the continents, and their mutability (inconstancy). The hot-spot theory may prove useful in explaining（）
Scattered around the globe are more than 100 small regions of isolated volcanic activity known to geologists as hot spots. Unlike most of the world’s volcanoes, they are not always found at the boundaries of the great drifting plates that make up the earth’s surface. On the contrary, many of them lie deep in the interior of a plate. Most of the hot spots move only slowly, and in some cases the movement of the plates past them has left trails of dead volcanoes. The hot spots and their volcanic trails are milestones that mark the passage of the plates.That the plates are moving is now beyond dispute. Africa and South America, for example, are moving away from each other as new material is injected into the sea floor between them. The complementary coastlines and certain geological features that seem to span the ocean are reminders of where the two continents were once joined. The relative motion of the plates carrying these continents has been constructed in detail, but the motion of one plate with respect to another cannot readily be translated into motion with respect to the earth’s interior. It is not possible to determine whether both continents are moving in opposite directions or whether one ocean is stationary and the other is drifting away from it. Hot spots, anchored in the deeper layer of the earth, provide the measuring instruments needed to resolve the question. From an analysis of the hot-spot population it appears that it has not moved during the 30 million years.The significance of hot spots is not confined to their role as a frame of reference. It now appears that they also have an important influence on the geophysical processes that propel the plates across the globe. When a continental plate comes to rest over a hot spot, the material rising from deeper layers creates a broad dome. As the dome grows, it develops deep fissures (cracks); in at least a few cases the continent may break entirely along some of these fissures, so that the hot spot initiates the formation of new ocean. Thus just as earlier theories have explained the mobility of the continents, so hot spots may explain the mobility of the continents, and their mutability (inconstancy). The passage is mainly about（）
Much of the language used to describe monetary policy, such as "steering the economy to a soft landing" or "a touch on the brakes", makes it sound like a precise science. Nothing could be further from the truth. The link between interest rates and inflation is uncertain. And there are long, variable lags before policy changes have any effect on the economy. Hence the analogy that likens the conduct of monetary policy to driving a car with a blackened windscreen, a cracked rear-view mirror and a faulty steering wheel.Given all these disadvantages, central bankers seem to have had much to boast about of late. Average inflation in the big seven industrial economies fell to a mere 2.3% last year, close to its lowest level in 30 years, before rising slightly to 2.5% this July. This is a long way below the double-digit rates which many countries experienced in the 1970s and early 1980s.It is also less than most forecasters had predicted. The panel of economists which The Economist polls each month said that America’s inflation rate would average 3.5% in 1995. In fact, it fell to 2.6% in August, and is expected to average only about 3% for the year as a whole. In Britain and Japan inflation is running half a percentage point below the rate predicted at the end of last year. This is no flash in the pan; over the past couple of years, inflation has been consistently lower than expected in Britain and America.Economists have been particularly surprised by favorable inflation figures in Britain and the Unite States, since conventional measures suggest that both economies, and especially America’s, have little productive slack. America’s capacity utilization, for example, hit historically high levels earlier this year, and its jobless rate (5.6% in August) has fallen below most estimates of the natural rate of unemployment — rate below which inflation has taken off in the past.Why has inflation proved so mild The most thrilling explanation is, unfortunately, a little defective. Some economists argue that powerful structural changes in the world have up- ended the old economic models that were based upon the historical link between growth and inflation. According to the passage, which of the following is true（）
Much of the language used to describe monetary policy, such as "steering the economy to a soft landing" or "a touch on the brakes", makes it sound like a precise science. Nothing could be further from the truth. The link between interest rates and inflation is uncertain. And there are long, variable lags before policy changes have any effect on the economy. Hence the analogy that likens the conduct of monetary policy to driving a car with a blackened windscreen, a cracked rear-view mirror and a faulty steering wheel.Given all these disadvantages, central bankers seem to have had much to boast about of late. Average inflation in the big seven industrial economies fell to a mere 2.3% last year, close to its lowest level in 30 years, before rising slightly to 2.5% this July. This is a long way below the double-digit rates which many countries experienced in the 1970s and early 1980s.It is also less than most forecasters had predicted. The panel of economists which The Economist polls each month said that America’s inflation rate would average 3.5% in 1995. In fact, it fell to 2.6% in August, and is expected to average only about 3% for the year as a whole. In Britain and Japan inflation is running half a percentage point below the rate predicted at the end of last year. This is no flash in the pan; over the past couple of years, inflation has been consistently lower than expected in Britain and America.Economists have been particularly surprised by favorable inflation figures in Britain and the Unite States, since conventional measures suggest that both economies, and especially America’s, have little productive slack. America’s capacity utilization, for example, hit historically high levels earlier this year, and its jobless rate (5.6% in August) has fallen below most estimates of the natural rate of unemployment — rate below which inflation has taken off in the past.Why has inflation proved so mild The most thrilling explanation is, unfortunately, a little defective. Some economists argue that powerful structural changes in the world have up- ended the old economic models that were based upon the historical link between growth and inflation. From the passage we learn that（）
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