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. - Fact
Nevertheless, some indication of their size can be inferred from spectrographic analyses of Jupiter’s outer atmosphere. - Opinion. It's in the same direction as the main conclusion.
After the fragments’ entry, these analyses revealed unprecedented traces of sulfur. - Fact
The fragments themselves almost certainly contained no sulfur, but astronomers believe that the cloud layer below Jupiter’s outer atmosphere does contain sulfur. - belief of astronomers/opinion
Since sulfur would have seeped into the outer atmosphere if comet fragments had penetrated this cloud layer, - Premise
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. - main conclusion
In the astronomer’s argument, the two portions in boldface play which of the following roles?
A. The first is a claim that the astronomer seeks to show is true (the first is not a claim. It's just a fact); the second acknowledges a consideration that weighs against the truth of that claim. (BF1 and BF2 go in the same direction). Weigh against is wrong.
B. The first is a claim that the astronomer seeks to show is true (the first is not a claim. It's just a fact); the second provides evidence in support of the truth of that claim. (It is a premise that supports the main conclusion and not the BF1 fact)
C. The first and the second are each consideration advanced in support of the conclusion of the argument.- ok
D. The first provides evidence in support of the conclusion of the argument (ok); the second is that conclusion (No. It is a premise)
E. The first is a circumstance for which the astronomer seeks to provide an explanation (ok); the second acknowledges a consideration that weighs against the explanation provided by the astronomer. (BF1 and BF2 go in the same direction). Weigh against is wrong.