Astronomer: Observations of the Shoemaker-Levi comet onits collision course with Jupiter showed that the comet broke into fragmentsbefore entering Jupiter's atmosphere in 1994, but they did not show how bigthose fragments were. In hopes ofgaining some indication of the fragments' size, astronomers studiedspectrographic analyses of Jupiter's outer atmosphere. These analyses revealed unprecedented tracesof sulfur after the fragments' entry.Thefragments themselves almost certainly contained no sulfur, but many astronomersbelieve that the cloud layer below Jupiter's outer atmosphere does containsulfur. Since sulfur would haveseeped into the outer atmosphere if comet fragments had penetrated this cloudlayer, it is likely that some of thefragments were at least large enough to have passed through Jupiter's outeratmosphere without being burned up.
In the astronomer's argument, the two portions in boldface play which of the followingroles?
(A) The first presents a circumstance for which theastronomer offers an explanation; the second is part of that explanation.
(B) The first acknowledges a consideration that weighsagainst the conclusion of the argument; the second is that conclusion.
(C) The first acknowledges a consideration that weighsagainst the conclusion of the argument; the second provides evidence in supportof that conclusion.
(D) The first provides evidence in support of theconclusion of the argument; the second acknowledges a consideration that weighsagainst that conclusion.
(E) The first is a judgment advanced in support of theconclusion of the argument; the second is that conclusion.
思路：A：排除，因为它说第二句话是Part of that explanation;