The author of this letter concludes that a wordwide decline in the number of amphibians is the indicateion,or result, of global air and water pollution.To support this assertion the author first notes a decline in amphibians in Yosemite Park between 1915 and 1992, and acknowledges that trout, which eat amphibian eggs, were intruduced in there in 1925. But, the author then claims that the intruduction of trout cannot be the reason for the decline in Yosemite Park because the introducion of trout in Yosemite does not explain the worldwide decline. I find this argument logically unconvincing in three critical respects. First, the author falis to provide any envidence to refute the strong inference that the decline in the number of amphibians was indeed caused by trout. Because the author dose not provide no affirmative evidence that pollution-- or some other phenomenon-- was instead the reason for the decline, the author's board assertion that wordwide decline in amphibians indicates global pollution is entirely unconvicing. Seconde, even if I were concede that the intruduction of trout was not the couse of Yosemite's amphibian decline, the author provide the decline was caused by pollution-- rather than some other phenomenon. Perhaps some other environmental factor was instead the cause. Without ruling out all orther possible explanations the author cannot covince me that pollution is the cause of the worldwide amphibian decline-- or even the decline in Yosemite alone. Thirdly, even if I were concede that pollution caused Yosemite's amphibians decline, this single sample is insufficient to draw any general conclusion about the reason for wordwide amphibian decline. It is entirely possible that the cause-and-effect relationships in Yosemite are not typical of the world in general. Without addittional samples from diverse geographic locations, I cannot accept the author's sweeping generalization about the decline of amphibians and global pollution. In sum, the scant evidence the author cites proves nothing about the reason for the general decline of amphibians wordwide; in fact, this evidence only serves to refute the author's own argument. To strengthen the argument the author should examine all changes occuring in Yosemit between 1915 and 1992, nad shouw that air and water pollution have at least contributed to the park's amphibian decline. In any event, the author must provide data about amphibian population changes and pollution at diverse geographical locations; and this data must show a strong inverse correlation between levels of air and water pollution and amphibian population worldwide.

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TOPIC: ARGUMENT150 - The following is a letter to the editor of an environmental magazine.

"The decline in the numbers of amphibians worldwide clearly indicates the global pollution of water and air. Two studies of amphibians in Yosemite National Park in California confirm my conclusion. In 1915 there were seven species of amphibians in the park, and there were abundant numbers of each species. However, in 1992 there were only four species of amphibians observed in the park, and the numbers of each species were drastically reduced. The decline in Yosemite has been blamed on the introduction of trout into the park's waters, which began in 1920 (trout are known to eat amphibian eggs). But the introduction of trout cannot be the real reason for the Yosemite decline because it does not explain the worldwide decline." WORDS: 274 TIME: 0:38:42 DATE: 2009-1-18

In this argument, the arguer concludes that the decline in the numbers of amphibians in Yosemite National Park in California indicates the global pollution of water and air. In addition, the arguer reasons that two studies shows that the number of species of amphibians in this park were drastically reduced between 1915 to 1992. This line of reasoning is flawed in several aspects. First of all, as the arguer claimed, the decline in Yosemite has been blamed on the introduction of trout into the park's waters in 1920. However, the aruger unfairly assumes that the introduction of trout brought no influence about the species reduce. It is possible that the trout ate much amphibian's eggs in these years and badly affects this area's eco-balance. In addition, the arguer attempts to establish a causal relationship between two matters: the amphibians reduced in Yosemite park and the global pollution of water and air. What's more, the evidence which the arguer used is the one prviousely used as a conclusion. Finally, the aruger omits several other concers that should be addressed. For example, the data about the park's temperture and humility changed between 1915 to 1992, the number of the trout in the recent years, the number of amphibians in other park between 1915 to 1992. In summary, the conclusion reached in this argument is invalid and misleading. To make the argument more convicing, the arguer would have to prove that the number of the amphibians in other park shows the same decline trendency. Moreover, I wolud suspend my judgement about the credibility of the recommendation until the arguer can provide concrete evidence that I notice before.

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In this argument, the arguer concludes that the respondents in the first study had misrepresented their reading habits. To support the conclusion, the arguer point out that a follow-up study shows that the Leeville citizens checked out of each of the public libraries in Leeville was the mystery novel, not the literary classics as Leeville respondents claimed before.This argument suffers from serveral critical fallacies. First of all, aruger fails to provided the details of the respondents. How the researchers found these respondents? The author assumes that the first respondents may respondented the whole Leeville citizens. In fact, with no solid evidence, this assumption is weak. Maybe, there are many dissimilarities between the respondents and the Leeville residents. In addition, the arguer fails to rule out the possibility that the most frequently checked out books may not be the type of book citizens preffered. It is possible that there are more mystery novels in these libraries in Leeville than other type of book. Thus it has much more probabilits to be checked out. Finally, the argument omits serveral other concerns that should be addressed. For example, which group of people lived nearby the public libraries, how long time the next study continue. To conclude, this argument is not persuasive as it stands. Before we accept the conclusion, the arguer must present more facts to prove that the two studies has a utterly link. To solidify the argument, the arguer wolud have to provide more evidence concering about the details in these two studies.