In the argument given above, the two portions in boldface play which of the following roles? A. The first is a claim that challenges the main conclusion; the second is the main conclusion. B. The first is a judgment made by the argument about a certain explanation; the second is that explanation. C. The first is an observation that calls into question an observed phenomenon; the second is the main conclusion of the argument. D. The first is a claim that the argument sets out to prove; the second limits the extent of this claim. E. The first is an intermediate conclusion; the second is the primary conclusion.