In 1994, a team of scientists led by David Mckay began studying the meteorite ALH84001, which had been discovered in Antarctica in 1984. Two years later, the McKay team announced that ALH84001, which scientists generally agree originated on Mars, contained compelling evidence that life once existed on Mars. This evidence includes the discovery of organic molecules in ALH84001, the first ever found in Martian rock. Organic molecules—complex, carbonbased compounds—form the basis for terrestrial life. The organic molecules found in ALH84001 are polycyclic aromatic hydrocarbons, or PAH’s. When microbes die, their organic material often decays into PAH’s.
Skepticism about the McKay team’s claim remains, however. For example, ALH84001 has been on earth for 13,000 years, suggesting to some scientists that its PAH’s might have resulted from terrestrial contamination. However, McKay’s team has demonstrated that the concentration of PAH’s increases as one looks deeper into ALH84001, contrary to what one would expect from terrestrial contamination. The skeptic’s strongest argument, however, is that processes unrelated to organic life can easily produce all the evidence found by McKay’ s team, including PAH’s. For example, star formation produces PAH’s. Moreover, PAH’s frequently appear in other meteorites, and no one attributes their presence to life processes. Yet McKay’s team notes that the particular combination of PAH’s in ALH84001 is more similar to the combinations produced by decaying organisms than to those originating form nonbiological processes.
The passage suggest that if a meteorite contained PAHs that were the result of terrestrial contamination, then one would expect which of the following to be true?
推理题当前版本由 703313krfq 更新于2021-04-17 12:38:16 感谢由 703313krfq 对此题目的解答所做出的贡献。
关键词 terrestrial contamination，定位到For example, ALH84001 has been on earth for 13,000 yea。。。 contamination. However, McKay’s team has demonstrated that the concentration of PAH’s increases as one looks deeper into ALH84001, contrary to what one would expect from terrestrial contamination.
选项A 题目是把陨石上PAH的来源是 terrestrial contamination造成的作为原因，推出后果，而13000是推出terrestrial contamination的原因不是结果，排除
选项C nonbiological processes.层次未提及
选项D other meteorites contain未提及，无关比较
根据terrestrial contamination定位第二段for example，后一句concetration是关键词
定位第二段however后面：Mck的团队证明PAHs不是terrestrial contamination的产物，即深入ALH，PAH的浓度增加。 题目问证明PAHs是terrestrial contamination的产物，即原文取非，只有E符合