Assumption. The correct answer choice is (E)
The stimulus is about Kim’s argument which concerns electric cars versus traditional gas powered cars. Her conclusion (the last sentence) is that even if all gas-powered cars were replaced with electric cars fossil fuel pollution would not decrease, it would just be replacing one source of pollution for another.
The premises that she uses to support this conclusion are:
- 1. “It takes electricity to recharge batteries and most of our electricity is generated by burning polluting fossil fuels.”
2. Increasing the number of electric cars would cause an increase in the number of power plants since current ones are running at maximum capacity.
Answer Choice (A): This is irrelevant as the argument in the stimulus does not depend on whether or not the total number of cars on the road increase or decrease. What we already know is that Kim has already accounted for an increase in the number of electric cars, which can be found in the third sentence of the stimulus. And that is all that is needed for her conclusion to be valid.
Answer Choice (B): Once again an irrelevant assumption. Nowhere in the stimulus does Kim make any claims about how significantly do gas powered cars contribute to fossil fuel pollution. This does not affect the conclusion that electric cars produce fossil fuel pollution through power plants.
Answer Choice (C): This answer choice may be tempting but we have to be aware of what the conclusion actually is. Kim does not make any claims about whether it is right to replace gas powered cars with electric ones; she just concludes that electric cars would contribute to fossil fuel pollution. And so we see that this is not a necessary assumption.
Answer Choice (D): Another unnecessary assumption. We don’t care if electric cars pollute while being operated; that is not the issue. The argument rests on the idea that the pollution comes from the power plants that will be built to supply the electric cars.
Answer Choice (E): This is the correct answer choice. Kim’s conclusion is based on the premise that fossil fuel pollution will remain relatively the same because electric cars would necessitate the building of more power plants. In turn these power plants would contribute to fossil fuel pollution because they burn fossil fuels. And that is where the assumption lies: That at least some of these new plants would burn fossil fuels. Negating (E) by saying that “None of the generating facilities built…would be a type that burns fossil fuel,” severely weakens the conclusion because if they don’t burn fossil fuel they clearly won’t be contributing to fossil fuel pollution.