PrepTest 118, Section 4, Question 7
A typical gasoline-powered lawn mower emits about as(42 more words not shown)
Which one of the following,(9 more words not shown)
- ALawns help to(7 more words not shown)
- BElectric lawn mowers(11 more words not shown)
- CProducing the power(20 more words not shown)
- DMost manufacturers of(16 more words not shown)
- ELawn mowers are(9 more words not shown)
Reading the argument
The electric mower doesn't emit pollutants while I use it. Where does its electricity come from? A power plant could be creating pollution somewhere else. Moving the emissions away from the lawn wouldn't automatically reduce the total. Manufacturing the electric mower could raise another question about pollution. I'm open to the proposed benefit, but I want the comparison to include more than what comes out of the mower itself.
The passage gives us a useful benchmark: running a typical gasoline mower for an hour produces about as much air pollution as running a car for an hour. We can use that comparison if an answer talks about the electric mower's power supply.
What we’re looking for
We're asked to strengthen the recommendation. I'd like reassurance that switching to electricity doesn't bring pollution costs that cancel the benefit. In particular, producing the electricity should be cleaner than running the gasoline mower. A helpful answer doesn't have to settle every concern about manufacturing and power generation; addressing a real gap in the comparison would move the argument forward.
Working the answers
- A
The effect of lawns on the air doesn't distinguish the two ways of mowing them. We could have the same lawn and cut it with either mower. A gives no reason to think the electric option produces less pollution.
- B
Higher purchase and maintenance costs might make electric mowers harder to afford. But the claimed benefit is reduced air pollution, and the recommendation already says to switch when feasible. An expense comparison doesn't establish the environmental advantage we're being asked to support.
- CCorrect
Now we can compare the electricity's pollution with the gasoline mower's pollution. Producing an hour's worth of power for the electric mower causes less air pollution than an hour of driving a car. The passage tells us that the car and a typical gasoline mower emit about the same amount per hour. So C supports the conclusion that powering the electric mower is cleaner than running the gasoline one.
This addresses the concern about pollution being created at the power plant. It doesn't have to show that electricity is perfectly clean; less pollution is enough to support a reduction.
- D
Trying to redesign gasoline mowers doesn't tell us what the redesigns will accomplish. Even if later models become cleaner, that wouldn't establish a present advantage for electric mowers. This doesn't support the recommendation to choose electric ones now.
- E
Annual mower use versus annual automobile use isn't the choice at issue. We're comparing two ways to do the mowing, not deciding whether mowers or cars contribute more pollution over a year. The hourly car comparison in the passage is useful because it lets C compare the power sources; E supplies a different comparison.
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