PrepTest 143, Section 4, Question 17
Near many cities, contamination of lakes and rivers(34 more words not shown)
The statement that contamination of(23 more words not shown)
- AIt is a(17 more words not shown)
- BIt is cited(17 more words not shown)
- CIt is a(21 more words not shown)
- DIt is a(16 more words not shown)
- EIt is stated(11 more words not shown)
Reading the argument
The water carries the pollutants. Does that make the water itself the polluter?
At first, the comparison with industrial discharge makes me wonder where the argument is headed. Having more contamination from runoff wouldn't make industrial pollution harmless. But the author makes a different claim: water itself is among the biggest polluters.
The explanation about oil gives me a reason to question that wording. Rainwater picks up pollutants as it crosses buildings and pavement, then carries them into lakes and rivers. That doesn't mean pure water is contaminating the lakes. The harmful material being carried still matters.
What we’re looking for
The question asks about the role of the opening comparison, so set that objection aside and follow the author's reasoning. The author uses the large amount of contamination carried by runoff to support calling water a major polluter. The comparison is evidence for the final claim.
Working the answers
- A
This reverses the direction. The author isn't using “water is a major polluter” to prove the comparison with industrial discharge. The comparison is offered first as a reason to believe that water should count as a major polluter.
- B
The comparison could make us wonder about the seriousness of runoff pollution, but the author's stated conclusion identifies water as a polluter. It doesn't make a separate judgment that runoff pollution is the more serious problem. B substitutes a different conclusion for the one actually drawn.
- C
Learning that runoff picks up oil doesn't establish that its contamination exceeds industrial discharge. We would still need information about how much each source contributes. The opening comparison is supplied as a fact, rather than inferred from the later description of how runoff gathers pollutants.
- DCorrect
The opening statement is a premise supporting the conclusion that water itself is among the biggest water polluters. Its comparison supplies the scale: runoff carries more contamination than industrial discharge near many cities. The author uses that scale to support “among the biggest,” while the next sentence explains how the water picks up the pollutants.
- E
The sentence makes a broad comparison between two sources of contamination. It isn't simply introducing a typical example of city pollution. Its job in this argument is to support the claim about the importance of water as a carrier the author calls a polluter.
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