Assumption. The correct answer choice is (B)
The structure of the argument is as follows:
- Premise: There is only so much metal ore available.
Subconclusion/ Premise: Ultimately we must either do without or turn to renewable resources to take its place.
Conclusion: The current pattern of human consumption of resources, in which we rely on nonrenewable resources, for example metal ore, must eventually change.
At first glance the argument does not seem to have any holes. This would suggest a Defender answer is coming, and indeed that is the case.
Answer choice (A): The author does not need to assume this statement because the stimulus specifically indicates that “we must either do without or turn to renewable resources.” Since doing without is an option, the author is not assuming there are renewable replacements for all nonrenewable resources currently being consumed.
Answer choice (B): This is the correct answer choice. This answer defends the conclusion that the consumption pattern must change by indicating that it would not be possible to simply replace one nonrenewable resource with another nonrenewable resource. If this answer did not make sense at first glance, you should have noted the negative language and then negated the answer. Using the Assumption Negation Technique, the following would clearly attack the conclusion: “We can indefinitely replace exhausted nonrenewable resources with other nonrenewable resources.” If the nonrenewable resources can be indefinitely replaced, why do we need to change our consumption habits?
Answer choice (C): The author’s argument concerns changing current consumption habits. Although the author does suggest turning to renewable resources, this alone would represent a change. The author does not make a long-term assumption that renewable resources can never be depleted. When faced with the negation of the answer choice, the author would likely reply: “If that eventuality does occur, then perhaps we will have to do without. In the meantime, we still need to change our consumption habits.” As you can see, the negation has not undermined the author’s position, and so this answer is incorrect.
Answer choice (D): The author does not make statements or assumptions about actual consumption patterns in the near future, only statements regarding what must eventually occur.
Answer choice (E): This answer, when rephrased to eliminate the double negative, reads as “Ultimately we must have nonrenewable resources.” Because this answer hurts the argument, the answer is incorrect.