In the argument given, the two portions in boldface play which of the following roles? A. The first is a claim made by the argument in support of a certain position; the second is that position. B. The first is a judgment made by the argument about a certain explanation; the second is that explanation. C. The first expresses the argument's dismissal of an objection to the position it seeks to establish; the second is that position. D. The first sums up the argument's position with regard to a certain hypothesis; the second provides grounds for that position. E. The first is a concession by the argument that its initial formulation of the position it seeks to establish requires modification; the second presents that position in a modified form.