PrepTest 140, Section 2, Question 12
Though Earth's human population is increasing, it currently(32 more words not shown)
Which one of the following,(8 more words not shown)
- APopulation growth trends(8 more words not shown)
- BThe amount of(16 more words not shown)
- CNot all of(11 more words not shown)
- DIf Earth's population(10 more words not shown)
- EThe percentage of(18 more words not shown)
Reading the argument
There may be plenty of fresh water on Earth. Is it where people can use it?
Imagine a large supply in a remote part of northern Canada and a growing population in a dry part of Arizona. Having water in the first place doesn't automatically supply the people in the second. This is a hypothetical distribution problem, not a claim about those places' actual water supplies.
What we’re looking for
The author treats a large unused global supply as a reason to dismiss near-term shortages. But a shortage needn't mean that humanity has used every drop on the planet. It can mean that the people who need water can't obtain enough of it where they live. To weaken the argument, I'd look for a reason that total supply isn't the same as usable supply for the relevant population.
Working the answers
- A
The warning is conditional on population-growth trends not changing. We can ask what would happen under those trends even if predicting them is difficult. Uncertainty about forecasts doesn't expose the argument's assumption that a large total water supply prevents shortages.
- BCorrect
Available fresh water varies significantly from region to region. That undermines the move from a reassuring global total to a reassuring conclusion for everyone. Water plentiful in one region may not meet the needs of people in another.
B doesn't have to prove that a specific city will run out next year. It gives us a reason why unused water somewhere on Earth doesn't settle whether people elsewhere face shortages, which is enough to weaken the argument's basis for dismissing the warning.
- C
Some people declining to conserve water doesn't by itself show that the apparently abundant supply is inadequate. We'd need to know how their use compares with what is available to them. C supplies neither that comparison nor the distribution problem that B identifies.
- D
Eventually isn't the near future. The population might exceed available resources hundreds or thousands of years from now without contradicting the author's claim about impending water shortages. The timing is essential to this argument.
- E
A faster increase in agriculture's share than in industry's share doesn't tell us whether total water use will exceed the water available. The distribution of uses isn't enough; we need information about whether the relevant supply can meet people's needs.
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