提问！大全GMAT63-26-6

xdlei

大全 GMAT63篇-26-6

In choosing a method for determining climatic conditions that existed in the past, paleoclimatologists invoke four principal criteria. First, the material—rocks, lakes, vegetation, etc.—on which the method relies must be widespread enough to provide plenty of information, since analysis of material that is rarely encountered will not permit correlation with other regions or with other periods 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 by modern physical or chemical means. Third, at least some of the material must have retained the signal unaffected by subsequent changes in the environment. Fourth, it must be possible to determine the time at which the inferred climatic conditions held. This last criterion is more easily met in dating marine sediments, because 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, because sedimentation is much less continuous in continental regions, estimating the age of a continental bed from the known ages of beds above and below is more risky.

In choosing a method for determining climatic conditions that existed in the past, paleoclimatologists invoke four principal criteria. First, the material—rocks, lakes, vegetation, etc.—on which the method relies must be widespread enough to provide plenty of information, since analysis of material that is rarely encountered will not permit correlation with other regions or with other periods 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 by modern physical or chemical means. Third, at least some of the material must have retained the signal unaffected by subsequent changes in the environment. Fourth, it must be possible to determine the time at which the inferred climatic conditions held. This last criterion is more easily met in dating marine sediments, because 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, because sedimentation is much less continuous in continental regions, estimating the age of a continental bed from the known ages of beds above and below is more risky.

6.     It can be inferred from the passage that an environmental signal found in geological material would not be useful to paleoclimatologists if it

(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

(E) was contained in a continental rather than a marine sequence

答案选D 我选E

为什么？请NN解释一下。。。

In choosing a method for determining climatic conditions that existed in the past, paleoclimatologists invoke four principal criteria. First, the material—rocks, lakes, vegetation, etc.—on which the method relies must be widespread enough to provide plenty of information, since analysis of material that is rarely encountered will not permit correlation with other regions or with other periods 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 by modern physical or chemical means. Third, at least some of the material must have retained the signal unaffected by subsequent changes in the environment. Fourth, it must be possible to determine the time at which the inferred climatic conditions held. This last criterion is more easily met in dating marine sediments, because 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, because sedimentation is much less continuous in continental regions, estimating the age of a continental bed from the known ages of beds above and below is more risky.

6.     It can be inferred from the passage that an environmental signal found in geological material would not be useful to paleoclimatologists if it

(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

(E) was contained in a continental rather than a marine sequence

答案选D 我选E

为什么？请NN解释一下。。。

nuj_am

Third, at least some of the material must have retained the signal unaffected by subsequent changes in the environment.

E项中lz一定是定位到了首段的最后一句,但是注意文中只是说continental的比较risky,但是没想题干中讲的not useful!!!

xdlei

哈。。。突然才发现我原来把“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 by modern physical or chemical means.”这句话中的reflects a change in climate一直记成change in environment了。。。疏忽啊疏忽。。。看来有时候回读一下原文还是非常必要的。。。

读文章时一定要仔细啊。。。