黑脸题大破解（7）

感兴趣的请参见: 黑脸题大破解
        系列贴

GWD5-Q20: (D)

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 a disproportionately large number of the
scientists who produce highly creative work beyond the age of forty entered
their field at an older age than is usual. 
Since by the age of forty the large majority of scientists have been
working in their field for at least fifteen years, the studies’ finding strongly suggests that the real reason why
scientists over forty rarely produce highly creative work is not that they have
simply aged but rather that they generally have spent too long in a given
field.

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

1. The first is the
        position that the argument as a whole opposes; the second is an objection that
        has been raised against a position defended in the argument.
2. The first is a claim
        that has been advanced in support of a position that the argument opposes;
        the second is a finding that has been used in support of that position.
3. The first is an
        explanation that the argument challenges; the second is a finding that has
        been used in support of that explanation.
4. The first is an explanation that the
        argument challenges; the second is a finding on which that challenge is based.
5. The first is an
        explanation that the argument defends; the second is a finding that has
        been used to challenge that explanation.

请总结1）
            2）
            3）
            4）
        点。

关键：联系词为challenges，其他的联系词都讲不通。比如A position； B position；C explanation； E explanation。
            

Defend：
        辩护答辩