PrepTest 130

Incorrect. The conclusion (and argument as a whole) is just about water use and restrictions, so other natural resources are out of scope.

Incorrect. The argument relies on freshwater supply being outstripped by demand in the future, making this answer wrong for two reasons. First, what happens in the future matters, not what has happened in the past. Second, the supply could go up as long as demand goes up more for the argument to work.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Necessary Premise

Stimulus Summary:
We've got enough water now, but the population is growing and will need more water, so we'll need restrictions on water use in the near future.

Answer Anticipation:
The conclusion here is making a prediction about the future, which is always suspect because things could change! While the argument does establish that the population will increase, thus increasing demand for water, there's no indication that something else won't change in order to meet that freshwater demand without restrictions. Maybe another source of water will be discovered, for instance.

When dealing with predictions about the future, potential changes always must be considered. Here, since the argument is concluding that the freshwater supply won't be able to meet demand in the future, it's assuming that sufficient increases to the water supply—a positive change—won't happen.

Answer Explanation:
This answer eliminates a possibility that would destroy the argument—that the freshwater supply increases enough to meet demand. Since it eliminates a possibility that can't happen if the argument is to work, this answer is correct.

Key Takeaway:
Predictions about the future are almost always suspect because they can't account for all potential changes that could happen. When an argument makes a prediction in the conclusion, start thinking about other changes that could affect that prediction.

Incorrect. This answer does address a possible way to increase water supply, so it should be considered (and it does strengthen the argument). However, it isn't a necessary assumption for the argument—attempts to synthesize could have an appreciable effect on the amount of water available but not lead to a sufficient increase to meet demand. Compare this answer to (C), where it specifically says that the increase in supply won't be enough to meet demand.

Incorrect. Even if previous water conservation methods have increased the water supply, the argument could still work—those methods may no longer be available.