Scientists typically do their most creative work before the age of forty. It is commonly thought that this happens because aging by itself brings about a loss of creative capacity. However, studies show that of scientists who produce highly creative work beyond the age of forty, a disproportionately large number entered their fi eld at an older age than is usual. Since by the age of forty the large majority of scientists have been working in their fi eld for at least fi fteen years, the studies’ fi nding strongly suggests that the real reason why scientists over forty rarely produce highly creative work is not that they have aged but rather that scientists over forty have generally spent too long in their fi eld.

In the argument given, the two portions in boldface play which of the following roles?

(A) The fi rst is a claim, the accuracy of which is at issue in the argument; the second is a conclusion drawn on the basis of that claim.

(B) The fi rst is an objection that has been raised against a position defended in the argument;

the second is that position.

(C) The fi rst is evidence that has been used to support an explanation that the argument challenges; the second is that explanation.

(D) The fi rst is evidence that has been used to support an explanation that the argument challenges; the second is a competing explanation that the argument favors.

(E) The fi rst provides evidence to support an explanation that the argument favors; the second is that explanation