单选题 Pollutants in the atmosphere can cause acid rain (rain with high acidity levels). While acid rain in itself cannot significantly affect the acidity of bodies of water into which it falls, it can greatly increase the acidity of nearby lakes by increasing the amount of decaying matter on a forest floor. A recent increase in the acidity of the water in Forest Lake, therefore, surely indicates that the rain failing nearby has become more acid.
Which of the following, if tree, most seriously weakens the argument?

A、 Even in areas without significant amounts of acid rain, most lakes in regions with vegetation similar to the vegetation around Forest Lake have acidity levels higher than those of other lakes
B、 Recent air-quality tests in the region around Forest Lake have revealed a slight increase in the amount of pollutants in the air
C、 Large-scale logging, which was recently begun in the forest surrounding Forest Lake, has increased the amount of decaying matter on the forest floor
D、 There is some disagreement among scientists about exactly how pollutants in the atmosphere cause acid rain
E、 Decaying matter exists on all forest floors and is an important factor in maintaining the healthy growth of the forests

【正确答案】 C

【答案解析】[解析] 本题作为GRE的No.5的“A"，not A→B”型的一道逻辑推理题的重考，背景内容完全一样，可参阅反对部分的讲解。