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题库 / Prep2007E1-CR-15
Astronomer: Observations of the Shoemaker-Levi comet on its collision course with Jupiter showed that the comet broke into fragments before entering Jupiter's atmosphere in 1994, but they did not show how big those fragments were. In hopes of gaining some indication of the fragments' size, astronomers studied spectrographic analyses of Jupiter's outer atmosphere. These analyses revealed unprecedented traces of sulfur after the fragments' entry. The fragments themselves almost certainly contained no sulfur, but many astronomers believe that the cloud layer below Jupiter's outer atmosphere does contain sulfur. Since sulfur would have seeped into the outer atmosphere if comet fragments had penetrated this cloud layer, it is likely that some of the fragments were at least large enough to have passed through Jupiter's outer atmosphere without being burned up.
In the astronomer's argument, the two portions in boldface play which of the following roles?
The first presents a circumstance for which the astronomer offers an explanation; the second is part of that explanation.
The first acknowledges a consideration that weighs against the conclusion of the argument; the second is that conclusion.
The first acknowledges a consideration that weighs against the conclusion of the argument; the second provides evidence in support of that conclusion.
The first provides evidence in support of the conclusion of the argument; the second acknowledges a consideration that weighs against that conclusion.
The first is a judgment advanced in support of the conclusion of the argument; the second is that conclusion.
天文学家的目的是想确定碎片的尺寸，而第二个粗体给出了一个结论，那就是碎片必须大到能够穿越大气层，所以第二个粗体是主结论，而第一个粗体实际上是一个事实前提，就是能确定碎片是含硫的，而木星的外围大气层是不含硫的，当碎片穿过大气层时会留下硫，所以如果在大气层中发现了硫，那说明碎片肯定是穿过了大气层。所以第一个粗体是支持结论的一个前提判断。
第一个粗体是观点型前提，认为碎片不含硫，而木星外围大气含硫
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