Assumption. The correct answer choice is (C)
This stimulus provides a series of statements involving the application of the law of supply and demand to global ecology. Global ecological problems are created when there is an imbalance between demand and sustainable supply, and global supply is inherently limited, but potential global demand is not. Based on these premises, the author concludes that any solution to global ecological problems would require reducing current human demand:
- Premise: Global ecological problems are created by an imbalance between demand and sustainable supply.
Premise: Global supply is limited, but potential global demand is not.
Conclusion: The only way to solve the natural tendency toward imbalance is to reduce current global demand.
Note the leap from a premise about the potential global demand to a conclusion about current global demand. The author apparently equates these two, with the assumption that current global demand causes the same tendency toward imbalance. As we seek an answer choice that addresses this issue, one way to verify the correct assumption is to apply the Assumption Negation Technique. When the negated version of an answer choice weakens (or destroys) the argument in the stimulus, we know that the given answer choice reflects an assumption on which the argument relies.
Answer choice (A): The stimulus discusses the natural tendency toward imbalance between demand and sustainable supply, which is the problem for which the author is suggesting a solution, so this assertion may run counter to the information provided in the stimulus. Even if supply and demand were to balance themselves out in the “long run,” it is unclear how long this might take. It is the general tendency toward imbalance that causes the problems the author seeks to solve.
If we apply the assumption negation technique to check our work, this is the negated version of this answer choice:
- “Supply and demand don’t tend to balance themselves out in the long run.”
Since this would not weaken or destroy the argument in the stimulus, this answer choice cannot reflect an assumption on which the author’s argument depends.
Answer choice (B): We don’t need to be able to determine the precise limitations on the earth’s sustainable supply in order for that supply to be outpaced by human demand, so this cannot be an assumption on which this argument relies. To check our work, we can apply the Assumption Negation technique and note whether the negated version of the answer choice would have any effect on the strength of the author’s argument:
- “It is not possible to determine the limitations of the earth’s sustainable supply.”
Even if this were impossible, this would not necessarily hamper our ability to deplete the supply completely and this would not affect the conclusion that human demand must be lowered as a part of any solution to the ecological problem, so this cannot be an assumption on which the argument is based.
Answer choice (C): This is the correct answer choice. For the argument’s conclusion to be logically drawn, we must assume that there is not only potential for demand to outpace supply—actual current demand must exceed the earth’s supply for there to be an imbalance which requires a solution. Applying the Assumption Negation technique to the answer choice would yield the following:
- “Human demand does not exceed supply.”
If this were the case, then lowering human demand as called for in the conclusion would not necessarily be so vital. Because the negated answer choice weakens the conclusion in the stimulus, this must be an assumption required by the argument.
Answer choice (D): If it were never possible to achieve a balance between environmental supply and human demand, there would be no long term solution to the global ecological problem, presuming that actual current demand were to outpace global supply. Since the stimulus discusses prospects for finding a solution, this answer choice cannot be an assumption on which the author’s argument relies. To check our work, we can apply the assumption negation technique by logically negating this answer choice:
- “It is sometimes possible to achieve a balance between the environmental supply and human demand.”
Since this would not weaken the argument in the stimulus in any way, this answer choice cannot reflect an assumption on which the conclusion of the stimulus relies.
Answer choice (E): The argument in the stimulus is based in part on the idea that there are no limits on potential human demands. If these demands did not decrease the earth’s supply, the problem that the author is looking to solve would not really exist, so this cannot be an assumption on which the argument relies. To check our work, we can again apply the assumption negation technique, to arrive at the following negated version of this answer choice:
- “Human consumption does decrease environmental supply.”
As we can see, the negated version of this answer choice has no weakening effect on the argument in the stimulus, so this cannot be an assumption on which the argument relies.