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Passage 26 (26/63)问题解决型（专业性科学文章）提出四个标准——提出问题In choosing a method for determining climatic conditions that existed in the past, paleoclimatologists invoke four principal criteria*2C. First, the material—rocks, lakes, vegetation, etc.—on which the method relies must be widespread*7 enough to provide plenty of information, since（小原因，可以暂时不看） analysis of material that is rarely encountered will not permit correlation with other regions or with other periods*7 of geological history. Second, in the process of formation, the material must have received an environmental signal that reflects a change in climate and that can be deciphered破译，解码 by modern physical or chemical means. Third, at least some of the material must have retained the signal *6unaffected by subsequent changes in the environment*6D. Fourth, it must be possible to determine the time at which the inferred climatic conditions held. This last criterion is more easily（比较句，很可能出题） met in dating marine sediments*1, because（小原因，暂时不用看） dating of only a small number of layers in a marine sequence allows the age of other layers to be estimated fairly reliably by extrapolation and interpolation. By contrast（强对比，一定要看）, because（小原因，暂时不用看，看后半句） sedimentation is much less continuous*1E in continental regions*1, estimating the age of a continental bed from the known ages of beds above and below is more risky.
解决方案一：古代湖泊水位法One very old（大-）method*2C used in the investigation of past climatic conditions involves the measurement of water levels in ancient lakes. 原因一In temperate regions温带地区, there are enough lakes for correlations between them to give us a reliable（小+，由于前面有大，所以后面一定有转折） picture. In arid and semiarid regions, on the other hand（转折）, the small number of lakes and the great distances between them reduce the possibilities for correlation. 原因二Moreover（大列举的非第一点）, since lake levels are controlled by rates of evaporation as well as（强调前者） by precipitation降水, the interpretation of such levels is ambiguous*5B（-）. For instance（与结论紧密相连，篇幅小，可以暂时不看）, the fact that lake levels in the semiarid southwestern United States*5 appear to have been higher during the last ice age than they are now was at one time attributed to increased precipitation. On the basis of snow-line elevations*3, however（其实还是紧跟上一个例子，可以暂时不看）, it has been concluded*3 that the climate then was not necessarily wetter than it is now, but rather that both summers and winters were cooler, resulting in reduced evaporation*3E.
解决方案二：花粉法Another problematic（大-） method is to reconstruct former climates on the basis of pollen profiles. The type of vegetation in a specific region is determined by identifying and counting（by doing通常都是很重要的内容） the various pollen grains found there. Although（转折的前半句可以不读） the relationship between vegetation and climate is not as direct as the relationship between climate and lake levels, the method often works well（小+） in the temperate zones. In arid and semiarid regions in which there is not much vegetation（-）, however, small changes in one or a few plant types can change the picture dramatically, making accurate correlations between neighboring areas difficult*8A（-） to obtain.
缺正确解决方案：看过程不看结果
1.Which of the following statements about the difference between marine and continental sedimentation*1 is supported by information in the passage?信息题（有定位，第一段最后一点）AD无，BC反
(A) Data provided by dating marine sedimentation is more consistent with 没提到researchers’ findings in other disciplines than is data provided by dating continental sedimentation.
(B) It is easier to estimate the age of a layer in a sequence of continental sedimentation 说反了than it is to estimate the age of a layer in a sequence of marine sedimentation.
(C) Marine sedimentation is much less widespread说反了 than continental sedimentation.
(D) Researchers are more often forced to rely on extrapolation没这么说 when dating a layer of marine sedimentation than when dating a layer of continental sedimentation.（E）
(E) Marine sedimentation is much more continuous*1E than is continental sedimentation.
2.Which of the following statements best describes the organization of the passage as a whole?主题题（写法性）
(A) The author describes a method for determining past climatic conditions and then offers specific examples of situations in which it has been used.
(B) The author discusses the method of dating marine and continental sequences and then explains how dating is more difficult with lake levels than with pollen profiles.
(C) The author describes the common requirements*2C of methods for determining past climatic conditions and then discusses examples of such methods*2C.问题解决型
(D) The author describes various ways of choosing a material for determining past climatic conditions and then discusses how two such methods have yielded contradictory data.（C）
(E) The author describes how methods for determining past climatic conditions were first developed and then describes two of the earliest known methods.
3.It can be inferred from the passage that paleoclimatologists have concluded*3 which of the following on the basis of their study of snow-line elevations*3 in the southwestern United States?
(A) There is usually more precipitation during an ice age because of increased amounts of evaporation.
(B) There was less precipitation during the last ice age than there is today.
(C) Lake levels in the semiarid southwestern United States were lower during the last ice age than they are today.
(D) During the last ice age, cooler weather led to lower lake levels than paleoclimatologists had previously assumed.（E）
(E) The high lake levels during the last ice age may have been a result of less evaporation rather than more precipitation*3E.
4.Which of the following would be the most likely topic for a paragraph that logically continues the passage?主题题（写法性）
(A) The kinds of plants normally found in arid regions
(B) The effect of variation in lake levels on pollen distribution
(C) The material best suited to preserving signals of climatic changes
(D) Other criteria invoked by paleoclimatologists when choosing a method to determine past climatic conditions（E）
(E) A third method for investigating past climatic conditions本文缺正确的解决方案
5.The author discusses lake levels in the southwestern United States*5in order to举例作用题（窍门法：illustrate, give/provide an example of；标准法：For instance, For example, such as, like——结论在前）
(A) illustrate the mechanics of the relationship between lake level, evaporation, and precipitation
(B) provide an example of the uncertainty*5B involved in interpreting lake levels
(C) prove that there are not enough ancient lakes with which to make accurate correlations
(D) explain the effects of increased rates of evaporation on levels of precipitation（B）
(E) suggest that snow-line elevations are invariably more accurate than lake levels in determining rates of precipitation at various points in the past
6.It can be inferred from the passage that an environmental signal*6（第二、第三个标准都讲到了，不过这里考的是第三个标准） found in geological material would not be useful to paleoclimatologists if it改善题的变体（回文中找优点——本文是要求、标准，然后取非）
(A) had to be interpreted by modern chemical means
(B) reflected a change in climate rather than a long-term climatic condition
(C) was incorporated into a material as the material was forming
(D) also reflected subsequent environmental changes*6D（D）
(E) was contained in a continental rather than a marine sequence
7.According to the passage, the material used to determine past climatic conditions must be widespread*7 for which of the following reasons?直接事实题（不要用非出题段落内容来解题）
I.Paleoclimatologists need to make comparisons between periods*7 of geological history.
II.Paleoclimatologists need to compare materials that have supported a wide variety of vegetation.
III.Paleoclimatologists need to make comparisons with data collected in other regions*7.
(A) I only
(B) II only
(C) I and II only
(D) I and III only（D）
(E) II and III only
8.Which of the following can be inferred from the passage about the study of past climates in arid and semiarid regions（第二段和第三段，定位太广，只能挨个答案看）?信息题BDE无，C反
(A) It is sometimes more difficult*8A to determine past climatic conditions in arid and semiarid regions than in temperate regions.
(B) Although in the past more research没讲过 has been done on temperate regions, paleoclimatologists have recently turned their attention to arid and semiarid regions.
(C) Although more information说反了 about past climates can be gathered in arid and semiarid than in temperate regions, dating this information is more difficult.
(D) It is difficult to study the climatic history of arid and semiarid regions because their climates have tended to vary more原因错了 than those of temperate regions.（A）
(E) The study of past climates in arid and semiarid regions has been neglected不对 because temperate regions support a greater variety of plant and animal life. |
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发表于 2010-8-17 18:06:26
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