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题目材料:
At a certain period in Earth`s history, its atmosphere contained almost no oxygen, although plants were producing vast quantities of oxygen. As a way of reconciling these two facts, scientists have hypothesized that nearly all of the oxygen being produced was taken up by iron on Earth`s surface. Clearly, however, this explanation is inadequate.New studies show that the amount of iron on Earth`s surface was not sufficient to absorb anywhere near as much oxygen as was being produced Therefore, something in addition to the iron on Earth`s surface must have absorbed much of the oxygen produced by plant life.
In the argument given, the two portions in boldface play which of the following roles?
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AThe first is a claim made by the argument in support of a certain position; the second is that position.
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BThe first is a judgment made by the argument about a certain explanation; the second is that explanation.
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CThe first expresses the argument`s dismissal of an objection to the position it seeks to establish; the second is that position.
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DThe first sums up the argument`s position with regard to a certain hypothesis; the second provides grounds for that position.
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EThe 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.
D显示答案