单选题 29. Rain-soaked soil contains less oxygen than does drier soil. The roots of melon plants perform less efficiently under the low-oxygen conditions present in rainsoaked soil. When the efficiency of melon roots is impaired, the roots do not supply sufficient amounts of the proper nutrients for the plants to perform photosynthesis at their usual levels. It follows that melon plants have a lower-than-usual rate of photosynthesis when their roots are in rain-soaked soil. When the photosynthesis of the plants slows, sugar stored in the fruits is drawn off to supply the plants with energy. Therefore, ripe melons harvested after a prolonged period of heavy rain should be less sweet than other ripe melons.
In the argument given, the two portions in boldface play which of the following roles? ______

A、 The first states the conclusion of the argument as a whole; the second provides support for that conclusion.
B、 The first provides support for the conclusion of the argument as a whole; the second provides evidence that supports an objection to that conclusion.
C、 The first provides support for an intermediate conclusion that supports a further conclusion stated in the argument; the second states that intermediate conclusion.
D、 The first serves as an intermediate conclusion that supports a further conclusion stated in the argument; the second states the position that the argument as a whole opposes.
E、 The first states the position that the argument as a whole opposes; the second supports the conclusion of the argument.

【正确答案】 C

【答案解析】 C：第一部分是一个客观原理，用来支持下一句话：光合作用所需能量不足。而这一间接结论又支持了下一句话：在雨水浸泡土壤中的植物的光合速率下降。因此选项C正确。
A：本文的结论只有最后一句，因此分号前错误，分号后正确。
B：分号前可以认为是正确的。但是全文顺承关系，不存在反驳，所以分号后错误。
D：分号前正确。全文是顺承关系，不存在反对，分号后错误。
E：全文是顺承关系，不存在反对。分号前错误，分号后可以认为是正确的。