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 asserts which of the following about the claim that ALH84001 originated on Mars ?
关键词ALH84001 originated on Mars定位到In 1994, a team of scientists led by David Mckay began studying the meteorite ALH84001, which had been discovered in Antarctica in 1984.
选项A initially 回文部分未提及
选项C It has been questioned by some skeptics 文章未提及
选项D It has been undermined by recent work on PAH’s.
选项E on Earth for 13,000 years.不是回文部分内容，排除
我是这样想的：scientists generally agree" ALH84001"originated on Mars,这个ALH84001来自火星是被大多数科学家认可的。而第二段的质疑是“ALH84001上有携带证明生物存在火星的物质”这个说法，题目问的则是“ALH84001来自火星”的相关说法，即选项B“it is not a dispute”是“generally agree”的同义转换
第二段反驳的是McKay的观点，这里ALH84001 originated on Mars的观点是其他scientist的观点
0 0 回复 2021-08-26 14:28:13
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. 定位在这
0 0 回复 2017-09-09 14:45:11