界线层型（Boundary stratotype）与单位层型（Unit stratotype）？

Text 4
The recent, apparently successful prediction by mathematical models of an appearance of El Nifio—the warm ocean current that periodically develops along the Pacific coast of South America -- has excited researchers. Jacob Bjerkness pointed out over 20 years ago how winds might create either abnormally warm or abnormally cold water in the eastern equatorial Pacific. Nonetheless, until the development of the models no one could explain why conditions should regularly shift from one to the other, as happens in the periodic oscillations between appearance of the warm El Nifio and the cold so-called anti-El Nifio. The answer, al least if the current model that links the behavior of the ocean to that of the atmosphere is correct, is to be found in the ocean.
It has long been known that during an El Niflo, two conditions exist: (1) unusually warm water extends along the eastern Pacific, principally along the coasts of Ecuador and Peru, and (2) winds blow from the west into the warmer air rising over the warm water in the east. These winds tend to create a feedback mechanism by driving the warmer surface water into a "pile" that blocks the normal upwelling of deeper, cold water in the east and further warms the eastern water, thus strengthening the wind still more. The contribution of the model is to show that the winds of an El Nifio, which raise sea level in the east, simultaneously send a signal to the west lowering sea level. According to the model, that signal is generated as a negative Rossby wave, a wave of depressed, or negative, sea level that moves westward parallel to the equator at 25 to 85 kilometers per day. Taking months to traverse the Pacific, Rossby waves march to the western boundary of the Pacific basin, which is modeled as a smooth wall but in reality consists of quite irregular island chains, such as the Philippines and Indonesia.
When the waves meet the western boundary, they are reflected, and the model predicts that Rossby waves will be broken into numerous coastal Kelvin waves carrying the same negative sea-level signal. These eventually shoot toward the equator, and then head eastward along the equator propelled by the rotation of the Earth at a speed of about 250 kilometers per day. When enough Kelvin waves of sufficient amplitude arrive from the western Pacific, their negative sea-level signal overcomes the feedback mechanism tending to raise the sea level, and they begin to drive the system into the opposite cold mode. This produces a gradual shift in winds, one that will eventually send positive sea-level Rossby waves westward, waves that will eventually return as cold cycle-ending positive Kelvin waves beginning another warming cycle.

According to the model, what normally signals the disappearance of an El Nifio（）

A:The arrival in the eastern Pacific of negative sea-level Kelvin waves. B:An increase in the speed at which negative Rossby waves cross the Pacific. C:A shift in the direction of the winds produced by the start of an anti-El Nifio elsewhere in the Pacific. D:The reflection of Kelvin waves after they reach the eastern boundary of the Pacific, along Ecuador and Peru.

Text 4
The recent, apparently successful prediction by mathematical models of an appearance of El Nifio—the warm ocean current that periodically develops along the Pacific coast of South America -- has excited researchers. Jacob Bjerkness pointed out over 20 years ago how winds might create either abnormally warm or abnormally cold water in the eastern equatorial Pacific. Nonetheless, until the development of the models no one could explain why conditions should regularly shift from one to the other, as happens in the periodic oscillations between appearance of the warm El Nifio and the cold so-called anti-El Nifio. The answer, al least if the current model that links the behavior of the ocean to that of the atmosphere is correct, is to be found in the ocean.
It has long been known that during an El Niflo, two conditions exist: (1) unusually warm water extends along the eastern Pacific, principally along the coasts of Ecuador and Peru, and (2) winds blow from the west into the warmer air rising over the warm water in the east. These winds tend to create a feedback mechanism by driving the warmer surface water into a "pile" that blocks the normal upwelling of deeper, cold water in the east and further warms the eastern water, thus strengthening the wind still more. The contribution of the model is to show that the winds of an El Nifio, which raise sea level in the east, simultaneously send a signal to the west lowering sea level. According to the model, that signal is generated as a negative Rossby wave, a wave of depressed, or negative, sea level that moves westward parallel to the equator at 25 to 85 kilometers per day. Taking months to traverse the Pacific, Rossby waves march to the western boundary of the Pacific basin, which is modeled as a smooth wall but in reality consists of quite irregular island chains, such as the Philippines and Indonesia.
When the waves meet the western boundary, they are reflected, and the model predicts that Rossby waves will be broken into numerous coastal Kelvin waves carrying the same negative sea-level signal. These eventually shoot toward the equator, and then head eastward along the equator propelled by the rotation of the Earth at a speed of about 250 kilometers per day. When enough Kelvin waves of sufficient amplitude arrive from the western Pacific, their negative sea-level signal overcomes the feedback mechanism tending to raise the sea level, and they begin to drive the system into the opposite cold mode. This produces a gradual shift in winds, one that will eventually send positive sea-level Rossby waves westward, waves that will eventually return as cold cycle-ending positive Kelvin waves beginning another warming cycle.

Which of the following would most seriously undermine the validity of the model of El Nifio mentioned（）

A:During some years El Nifio extends significantly farther along the coasts of Ecuador and Peru than during other years. B:During periods of unusually cool temperature along the eastern Pacific, an El Nifio is much colder than normal. C:The variations in the time it takes Rossby waves to cross the Pacific depend on the power of the winds that the waves encounter. D:The western boundary of the Pacific basin is so irregnlar that it hinders most coastal Kelvin waves from heading eastward.

One great benefit of the Web is that it allows us to move information online that now resides in paper form. Several states in America are using the Web in a profound way. You can apply for various permits or submit applications for business licences. Some states are putting up listings of jobs—not just state government jobs, but all the jobs available in the state. I believe, over time, that all the information that governments print, and all those paper forms they now have, will be moved on to the Internet. Electronic commerce notches up month-by-month too. It is difficult to measure, because a lot of electronic commerce involves existing buyers and sellers who are simply moving paperbased transactions to the Web. That is not new business. Microsoft, for example, purchases millions of dollars of PCs online instead of by paper. However, that is not a fundamental change; it has just improved the efficiency of an existing process. The biggest impact has occurred where electronic commerce matches buyers and sellers who would not previously have found each other. When you go to a book site and find an obscure book that you never would have found in a physical bookstore, that is a new type of commerce.
Today, about half of all PCs are still not connected to the Web. Getting communications costs down and making all the software simpler will bring in those people. And that, in turn, will move us closer to the critical mass that will make the Web lifestyle everyone’s lifestyle. One clement that people underestimate is the degree to which the hardware and software will improve. Just take one aspect: screen technology. I do my e-mail on a 20-inch liquid crystal display (LCD) monitor. It is not available at a reasonable price yet, but in two years it will be. In ten years, a 40-inch LCD with much higher resolution will be commonplace.
The boundary between a television set and a PC will be blurred because even the set-top box that you connect up to your cable or satellite will have a processor more powerful than what we have today in the most expensive PC. This will, in effect, make your television a computer.
Interaction with the Web also will improve, making it much easier for people to be involved. Today the keywords we use to search the Web often return to too many articles to sort through, many of them out of context. If you want to learn about the fastest computer chip available, you might end up getting responses instead about potato chips being delivered in fast trucks. In the future, we shall be either speaking or typing sentences into the computer. If you ask about the speed of chips, the result will be about computers, not potatoes. Speech recognition also means that you will be able to call in on a phone and ask if you have any new messages, or check on a flight, or check on the weather.
To predict that it will take over ten years for these changes to happen is probably pessimistic. We usually overestimate what we can do in two years and underestimate what we can do in ten. The Web will be as much a way of life as the car by 2008. Probably before.
The use of computer will be as common as the use of cars when ______.

A:computer and communication become simpler and cheaper B:electronic commerce causes a fundamental change C:the boundary between the computer and the TV disappears D:governments began to move administration on-line

Text 1
Many of the world’s big lakes are threatened by pollution or huge drainage schemes. But there is least one fairly bright spot. The Great Lakes and St. Lawrence river system between Canada and the United States, which together account for a fifth of the world’s non-polar fresh water, are much healthier than they were. Can they stay that way
Though Lake Michigan is wholly the United States, all five lakes are governed by the Boundary Waters Treaty of 1909, implemented by an independent bi-national joint commission. In 1978, both countries agreed to try to clean up the water in the lakes, several of which were heavily polluted. They have done so though in fact the improvement owes as much to economic change as to government action. Steel and other heavy industry have given way to cleaner industries and services, both in Ontario and in American lakeside states. The result: tests on fish and birds show residues of heavy metals have declined (though dangerous levels of mercury are still found), while in past ten years the rivers near Toronto have been successfully stocked with salmon.
There are still worries. One problem is farming. This uses much lake water 929% of the total that is withdrawn) from irrigation, while also polluting the lakes and river systems. The huge quantities of manure spread on farms in Ontario and Quebec also causes pollution, by running off the land into streams, rivers and then lakes.
Some scientists also worry that water levels will fall permanently. Climate change is likely to cut rainfall in the Great Lakes basin, while ever more water will be drawn from the lakes by a rising urban population. General consumption in the basin will increase by 25% in the next 25 years, according to a forecast by a consultant to the commission.
Other threats include some 140 exotic species of flora, fish and shellfish that have found their way into the lakes, some via ships’ ballast.. The zebra mussel from Eastern Europe is the most notorious and probably most damaging to the environment. It consumes a lot of oxygen (though it also helps to clean the water). Lastly, there is the hazardous prospect of decommissioning Ontario’s two dozen ageing nuclear reactors, which line the shores of Lake Ontario and Lake Huron.
Fortunately, the long history of successful co-operation between the two countries and among the local governments suggest these threats can be managed. Both governments have approved the commission’s plan to set up international watershed boards across the continent. These are to take a "holistic" approach to ecosystems. Maybe the Zebra mussel and the farm run- offs have met their match.

In the first two paragraphs, the author suggests（）

A:the bi-national joint commission has done its routine job. B:the Boundary Water Treaty of 1909 has become out-of-date. C:the huge drainage schemes are to blame for land run-offs. D:the economic change has contributed to environmental improvement.

Text 4 The recent, apparently successful prediction by mathematical models of an appearance of El Nifio—the warm ocean current that periodically develops along the Pacific coast of South America -- has excited researchers. Jacob Bjerkness pointed out over 20 years ago how winds might create either abnormally warm or abnormally cold water in the eastern equatorial Pacific. Nonetheless, until the development of the models no one could explain why conditions should regularly shift from one to the other, as happens in the periodic oscillations between appearance of the warm El Nifio and the cold so-called anti-El Nifio. The answer, al least if the current model that links the behavior of the ocean to that of the atmosphere is correct, is to be found in the ocean. It has long been known that during an El Niflo, two conditions exist: (1) unusually warm water extends along the eastern Pacific, principally along the coasts of Ecuador and Peru, and (2) winds blow from the west into the warmer air rising over the warm water in the east. These winds tend to create a feedback mechanism by driving the warmer surface water into a "pile" that blocks the normal upwelling of deeper, cold water in the east and further warms the eastern water, thus strengthening the wind still more. The contribution of the model is to show that the winds of an El Nifio, which raise sea level in the east, simultaneously send a signal to the west lowering sea level. According to the model, that signal is generated as a negative Rossby wave, a wave of depressed, or negative, sea level that moves westward parallel to the equator at 25 to 85 kilometers per day. Taking months to traverse the Pacific, Rossby waves march to the western boundary of the Pacific basin, which is modeled as a smooth wall but in reality consists of quite irregular island chains, such as the Philippines and Indonesia. When the waves meet the western boundary, they are reflected, and the model predicts that Rossby waves will be broken into numerous coastal Kelvin waves carrying the same negative sea-level signal. These eventually shoot toward the equator, and then head eastward along the equator propelled by the rotation of the Earth at a speed of about 250 kilometers per day. When enough Kelvin waves of sufficient amplitude arrive from the western Pacific, their negative sea-level signal overcomes the feedback mechanism tending to raise the sea level, and they begin to drive the system into the opposite cold mode. This produces a gradual shift in winds, one that will eventually send positive sea-level Rossby waves westward, waves that will eventually return as cold cycle-ending positive Kelvin waves beginning another warming cycle.

According to the model, what normally signals the disappearance of an El Nifio（）

A:The arrival in the eastern Pacific of negative sea-level Kelvin waves. B:An increase in the speed at which negative Rossby waves cross the Pacific. C:A shift in the direction of the winds produced by the start of an anti-El Nifio elsewhere in the Pacific. D:The reflection of Kelvin waves after they reach the eastern boundary of the Pacific, along Ecuador and Peru.

Text 4 The recent, apparently successful prediction by mathematical models of an appearance of El Nifio—the warm ocean current that periodically develops along the Pacific coast of South America -- has excited researchers. Jacob Bjerkness pointed out over 20 years ago how winds might create either abnormally warm or abnormally cold water in the eastern equatorial Pacific. Nonetheless, until the development of the models no one could explain why conditions should regularly shift from one to the other, as happens in the periodic oscillations between appearance of the warm El Nifio and the cold so-called anti-El Nifio. The answer, al least if the current model that links the behavior of the ocean to that of the atmosphere is correct, is to be found in the ocean. It has long been known that during an El Niflo, two conditions exist: (1) unusually warm water extends along the eastern Pacific, principally along the coasts of Ecuador and Peru, and (2) winds blow from the west into the warmer air rising over the warm water in the east. These winds tend to create a feedback mechanism by driving the warmer surface water into a "pile" that blocks the normal upwelling of deeper, cold water in the east and further warms the eastern water, thus strengthening the wind still more. The contribution of the model is to show that the winds of an El Nifio, which raise sea level in the east, simultaneously send a signal to the west lowering sea level. According to the model, that signal is generated as a negative Rossby wave, a wave of depressed, or negative, sea level that moves westward parallel to the equator at 25 to 85 kilometers per day. Taking months to traverse the Pacific, Rossby waves march to the western boundary of the Pacific basin, which is modeled as a smooth wall but in reality consists of quite irregular island chains, such as the Philippines and Indonesia. When the waves meet the western boundary, they are reflected, and the model predicts that Rossby waves will be broken into numerous coastal Kelvin waves carrying the same negative sea-level signal. These eventually shoot toward the equator, and then head eastward along the equator propelled by the rotation of the Earth at a speed of about 250 kilometers per day. When enough Kelvin waves of sufficient amplitude arrive from the western Pacific, their negative sea-level signal overcomes the feedback mechanism tending to raise the sea level, and they begin to drive the system into the opposite cold mode. This produces a gradual shift in winds, one that will eventually send positive sea-level Rossby waves westward, waves that will eventually return as cold cycle-ending positive Kelvin waves beginning another warming cycle.

Which of the following would most seriously undermine the validity of the model of El Nifio mentioned（）

A:During some years El Nifio extends significantly farther along the coasts of Ecuador and Peru than during other years. B:During periods of unusually cool temperature along the eastern Pacific, an El Nifio is much colder than normal. C:The variations in the time it takes Rossby waves to cross the Pacific depend on the power of the winds that the waves encounter. D:The western boundary of the Pacific basin is so irregnlar that it hinders most coastal Kelvin waves from heading eastward.

That fence over there forms the {{U}}boundary{{/U}} between our garden and our neighbours

A:dividing line B:frontier C:border D:front