The conclusion of the argument is "we can never run out of important natural resources."
Why? We are told that when the supply of one resource dwindles, alternative technologies make way for the use of different resources that will take the place of the dwindling resource, e.g. flint for arrowheads, trees usable for schooner masts, and good mules. So, since "new technologies constantly replace old ones" there will never be a dearth of important natural resources.
Remember, there are two ways to weaken an argument. You must either show that one of the premises is false, or that the conclusion does not necessarily follow.
Answer choice (E) states: "The biological requirements for substances like clean air and clean water are unaffected by technological change."
Answer choice (E) shows us that the conclusion of the argument does not necessarily follow. It gives us a couple examples of resources that cannot be replaced by technological change. Clean air and clean water are essential resources that cannot be replaced by technological change. Thus, it is not necessarily true that we can never run out of important natural resources since new technology cannot remedy the issue of a dwindling supply of clean water or clean air.
Therefore, answer choice (E) seriously undermines the conclusion.
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