Pollutants in the atmosphere can cause acid rain. 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 falling nearby has become more acid. Which of the following, if true, most seriously weakens the argument? 答案为Large-scale logging, which was recently begun in the forest surrounding Forest Lake, has increased the amount of decaying matter on the forest floor. 它还有一个选项为Even in areas without significantly 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.为什么不可以呢？ | 
