passage 7

The success of fluoride in combating dental decay is well established and, without a doubt, socially beneficial. However, fluoride's toxic properties have been known for a century. In humans excessive intake ( for adults, (5) over 4 milligrams per day) over many years can lead to skeletal fluorosis, a well-defined skeletal disorder, and in some plant species, fluoride is more toxic than ozone, sulfur dioxide, or pesticides. Some important questions remain.For example, the (10)precise lower limit at which the fluoride content of bone becomes toxic is still undetermined. And while fluoride intake from water and air can be evaluated relatively easily, it is much harder to estimate how much a given population ingests from foodstuffs because of the wide (15)variations in individual eating habits and in fluoride concentrations in foodstuffs. These difficulties suggest that we should by wary of indiscriminately using fluo- ride, even in the form of fluoride-containing dental products. 1. In the passage, the author is primarily concerned with (A) analyzing and categorizing (B) comparing and contrasting (C) synthesizing and predicting (D) describing and cautioning (E) summarizing and reinterpreting 2. The passage suggests that it would be easier to calculate fluoride intake from food if (A) adequate diets were available for most people. (B) individual eating habits were more uniform (C) the fluoride content of food was more varied (D) more people were aware of the fluoride content of food (E) methods for measuring the fluoride content of food were more generally agreed on 3. One function of the second paragraph of the passage is to (A) raise doubts about fluoride's toxicity (B) introduce the issue of fluoride's toxicity (C) differentiate a toxic from a nontoxic amount of fluoride (D) indicate that necessary knowledge of fluoride remains incomplete (E) discuss the foodstuffs that are most likely to contain significant concentrations of fluoride 4. The passage suggests which of the following about the effect of fluoride on humans? (A) The effect is more easily measured than is the effect of exposure to pesticides. (B) The effect of fluoride intake from water and air is relatively difficult to monitor. (C) In general the effect is not likely to be as harmful as the effect of exposure to sulfur dioxide. (D) An intake of 4 milligrams over a long period of time usually leads to a skeletal disorder in humans. (E) An intake of slightly more than 4 milligrams for only a few months is not likely to be life-threatening. PASSAGE 2 Although, recent years have seen substantial reductions in noxious pollutants from individual motor vehicles, the number of such vehicles has been steadily increasing consequently, more than 100 cities in the United States still have levels of carbon monoxide, particulate matter, and ozone (generated by photochemical, reactions with hydrocarbons from vehicle exhaust) that exceed legally established limits. There is a growing, realization that the only effective way to achieve, further reductions in vehicle emissions-short of a massive shift away from the private automobile-is to replace conventional diesel fuel and gasoline with cleaner-burning fuels such as compressed natural gas, liquefied petroleum gas, ethanol, or methanol. All of these alternatives are carbon- based fuels whose molecules are smaller and simpler than those of gasoline. These molecules burn more cleanly than gasoline, in part because they have fewer, if and , carbon-carbon bonds, and the hydrocarbons they do emit are less likely to generate ozone. The combustion of larger molecules, which have multiple carbon-carbon bonds, involves a more complex series of reactions. These reactions increase the probability of incomplete combustion and are more likely to release uncombusted and photochemically active hydrocarbon compounds into the atmosphere. On the other hand, alternative fuels do have drawbacks. Compressed natural gas would require that vehicles have a set of heavy fuel tanks-a serious liability in terms of performance and fuel efficiency---- and liquefied petroleum gas faces fundamental limits on supply. Ethanol and methanol, on the other hand, have important advantages over other carbon-based alternative fuels: they have a higher energy content per volume and would require minimal changes in the existing network for distributing motor fuel. Ethanol is commonly used as a gasoline supplement, but it is currently about twice as expensive as methanol, the low cost of which is one of its attractive features. Methanol's most attractive feature, however, is that it can reduce by about 90 percent the vehicle emissions that form ozone, the most serious urban air pollutant. Like any alternative fuel, methanol has its critics, Yet much of the criticism is based on the use of "gasoline clone" vehicles that do not incorporate even the simplest design improvements that are made possible with the use of methanol. It is true, for example, that a given volume of methanol provides only about one-half of the energy that gasoline and diesel fuel do; other things being equal, the fuel tank would have to be somewhat larger and heavier. However, since methanol- fueled vehicles could be designed to be much more efficient than "gasoline clone" vehicles fueled with methanol, they would need comparatively less fuel. Vehicles incorporating only the simplest of the engine improvements that methanol makes feasible would still contribute to an immediate lessening of urban air pollution. 1. The author of the passage is primarily concerned with (A) countering a flawed argument that dismisses a possible solution to a problem (B) reconciling contradictory points of view about the nature of a problem (C) identifying the strengths of possible solutions to a problem. (D) discussing a problem and arguing in favor of one solution to it (E) outlining a plan of action to solve a problem and discussing the obstacles blocking that plan. 2. According to the passage, incomplete combustion is more likely to occur with gasoline than with an alternative fuel because (A) the combustion of gasoline releases photochemically active hydrocarbons (B) the combustion of gasoline involves an intricate series of reactions (C) gasoline molecules have a simple molecular structure (D) gasoline is composed of small molecules. (E) gasoline is a carbon-based fuel 3. The passage suggests which of the following about air pollution? (A) Further attempts to reduce emissions from gasoline-fueled vehicles will not help lower urban air-pollution levels. (B) Attempts to reduce the pollutants that an individual gasoline-fueled vehicle emits have been largely unsuccessful. (C) Few serious attempts have been made to reduce the amount of pollutants emitted by gasoline-fueled vehicles. (D) Pollutants emitted by gasoline-fueled vehicles are not the most critical source of urban air pollution. (E) Reductions in pollutants emitted by individual vehicles have been offset by increases in pollution from sources other than gasoline-fueled vehicles. 4. Which of the following most closely parallels the situation described in the first sentence of the passage? (A) Although a town reduces its public services in order to avoid a tax increase, the town's tax rate exceeds that of other towns in the surrounding area. (B) Although a state passes strict laws to limit the type of toxic material that can be disposed of in public landfills, illegal dumping continues to increase. (C) Although a town's citizens reduce their individual use of water, the town's water supplies continue to dwindle because of a steady increase in the total population of the town. (D) Although a country attempts to increase the sale of domestic goods by adding a tax to the price of imported goods, the sale of imported goods within the country continues to increase. (E) Although a country reduces the speed limit on its national highways, the number of fatalities caused by automobile accidents continues to increase. 5. The author describes which of the following as the most appealing feature of methanol? (A) It is substantially less expensive than ethanol. (B) It could be provided to consumers through the existing motor fuel distribution system. (C) It has a higher energy content than other alternative fuels. (D) Its use would make design improvements in individual vehicles feasible. (E) Its use would substantially reduce ozone levels. 6. It can be inferred from the passage that a vehicle specifically designed to use methanol for fuel would (A) be somewhat lighter in total body weight than a conventional vehicle fueled with gasoline (B) be more expensive to operate than a conventional vehicle fueled with gasoline (C) have a larger and more powerful engine than a conventional vehicle fueled with gasoline (D) have a larger and heavier fuel tank than a "gasoline clone" vehicle fueled with methanol (E) average more miles per gallon than a "gasoline clone" vehicle fueled with methanol 7. It can be inferred that the author of the passage most likely regards the criticism of methanol in the last paragraph as (A) flawed because of the assumptions on which it is based (B) inapplicable because of an inconsistency in the critics' arguments. (C) misguided because of its exclusively technological focus (D) inaccurate because it ignores consumers' concerns (E) invalid because it reflects the personal bias of the critics PASSAGE 3 Many objects in daily use have clearly been influenced by science, but their form and function, their dimensions and appearance, were determined by technologists artisans, designers, inventors, and engineers---using non-scientific modes of thought. Many features and qualities of the objects that a technologist thinks about cannot be reduced to unambiguous verbal descriptions; they are dealt with in the mind by a visual, nonverbal process. In the development of Western technology, it has been non-verbal thinking, by and large, that has fixed the outlines and filled in the details of our material surroundings. Pyramids, cathedrals, and rockets exist not because of geometry or thermodynamics but because they were first a picture in the minds of those who built them. The creative shaping process of a technologist's mind can be seen in nearly every artifact that exists. For example, in designing a diesel engine, a technologist might impress individual ways of nonverbal thinking on the machine by continually using an intuitive sense of rightness and fitness. What would be the shape of the combustion chamber? Where should the valves be placed? Should it have a long or short piston? Such questions have a range of answers that are supplied by experience, by physical requirements, by limitations of available space, and not least by a sense of form. Some decisions, such as wall thickness and pin diameter, may depend on scientific calculations, but the nonscientific component of design remains primary. Design courses, then, should be an essential element in engineering curricula. Nonverbal thinking, a central mechanism in engineering design, involves perceptions, the stock-in-trade of the artist, not the scientist. Because perceptive processes are not assumed to entail "hard thinking," nonverbal thought is sometimes seen as a primitive stage in the development of cognitive processes and inferior to verbal or mathematical thought. But it is paradoxical that when the staff of the Historic American Engineering Record wished to have drawings made of machines and histoisometric views of industrial processes for its rical record of American engineering, the only college students with the requisite abilities were not engineering students, but rather students attending architectural schools. It courses in design, which in a strongly analytical engineering curriculum provide the background required for practical problemsolving, are not provided, we can expect to encounter silly but costly errors occurring in advanced engineering systems. For example, early models of high-speed railroad cars loaded with sophisticated controls were unable to operate in a snowstorm because a fan sucked snow into the electrical system. Absurd random failures that plague automatic control systems are not merely trivial aberrations; they are a reflection of the chaos that results when design is assumed to be primarily a problem in mathematics. 1. In the passage, the author is primarily concerned with (A) identifying the kinds of thinking that are used by technologists (B) stressing the importance of nonverbal thinking in engineering design (C) proposing a new role for nonscientific thinking in the development of technology (D) contrasting the goals of engineers with those of technologists (E) criticizing engineering schools for emphasizing science in engineering curricula 2. It can be inferred that the author thinks engineering curricula are (A) strengthened when they include courses in design (B) weakened by the substitution of physical science courses for courses designed to develop mathematical skills (C) strong because nonverbal thinking is still emphasized by most of the courses (D) strong despite the errors that graduates of such curricula have made in the development of automatic control systems (E) strong despite the absence of nonscientific modes of thinking 3. Which of the following statements best illustrates the main point of lines 1-28 of the passage? (A) When a machine like a rotary engine malfunctions, it is the technologist who is best equipped to repair it. (B) Each component of an automobile-for example, the engine or the fuel tank has a shape that has been scientifically determined to be best suited to that component's function (C) A telephone is a complex instrument designed by technologists using only nonverbal thought (D) The designer of a new refrigerator should consider the designs of other refrigerators before deciding on its final form. (E) The distinctive features of a suspension bridge reflect its designer's conceptualization as well as the physical requirements of its site. 4. Which of the following statements would best serve as an introduction to the passage? (A) The assumption that the knowledge incorporated in technological developments must be derived from science ignores the many nonscientific decisions made by technologists. (B) Analytical thought is no longer a vital component in the success of technological development. (C) As knowledge of technology has increased, the tendency has been to lose sight of the important role played by scientific thought in making decisions about form, arrangement, and texture. (D) A movement in engineering colleges toward a technician's degree reflects a demand for graduates who have the nonverbal reasoning ability that was once common among engineers. 5. The author calls the predicament faced by the Historic American Engineering Record "paradoxical" most probably because (A) the publication needed drawings that its own staff could not make (B) architectural schools offered but did not require engineering design courses for their students (C) college students were qualified to make the drawings while practicing engineers were not (D) the drawings needed were so complicated that even students in architectural schools had difficulty making them. (E) engineering students were not trained to make the type of drawings needed to record the development of their own discipline 6. According to the passage, random failures in automatic control systems are "not merely trivial aberrations" because (A) automatic control systems are designed by engineers who have little practical experience in the field (B) the failures are characteristic of systems designed by engineers relying too heavily on concepts in mathematics (C) the failures occur too often to be taken lightly (D) designers of automatic control systems have too little training in the analysis of mechanical difficulties (E) designers of automatic control systems need more help from scientists who have a better understanding of the analytical problems to be solved before such systems can work efficiently 7. The author uses the example of the early models of high-speed railroad cars primarily to (A) weaken the argument that modern engineering systems have major defects because of an absence of design courses in engineering curricula (B) support the thesis that the number of errors in modern engineering systems is likely to increase (C) illustrate the idea that courses in design are the most effective means for reducing the cost of designing engineering systems (D) support the contention that a lack of attention to the nonscientific aspects of design results in poor conceptualization by engineers (E) weaken the proposition that mathematics is a necessary part of the study of design 答案 八年级地理上册填图题岩土工程勘察试题省略号的作用及举例应急救援安全知识车间5s试题及答案 ： Passage 1: DBDE Passafe 2: CBACE EA Passage 3: BAEAE BD