Stem: Find an answer which undermines the likelihood that "economy boost" and "less pollution" cannot be achieved using incentives.
Premises:
1. Automobile emissions are a significant source of air pollutants
2. cars over five years old typically generate significantly greater amounts of pollutants than newer cars
3. Torinia has recently built its first automobile manufacturing plant
4. Most cars in Torinia are over five years.
Using these premises it can be concluded that if incentives are given then, old cars will be replaced, reducing pollution and since new cars are bought, the business of the manufacturing unbit will prosper and economy gets a boost.
So something has to be found out that will not lead to pollution reduction and economy boost. However, one thing should be remembered that economy factor is dependent on the buying of new cars which will take place only if the old cars are scrapped due to reason of pollution. Incentive will help buying of new cars which will reduce pollution and hence trigger the economy.
PoE:
(A) Without the implementation of the planned incentives, most Torinians who own an old car would be unlikely to buy a new car.
Out of Question. You have to find where the two benefits wont be achieved when incentives are used.
(B) Torinia's automobile plant manufactures car models that typically generate smaller amounts of air pollutants than most similarly sized car models manufactured elsewhere.
Thats good. It shall be a factor which shall reduce pollution and if incentives are there, people will buy and would boost the economy. But we are looking for a factor which shall undermine the likelihood that the two things can be achieved. This strengthens and not weakens the success of incentivizing.
(C) The new cars produced in Torinia are not likely to be exported to other countries.
How does it affect the success of incentivizing. If nothing better, it strengthens as most cars will be sold in Torinia after incentives.
(D) The largest source of atmospheric pollutants in Torinia is not automobile emissions, but emissions from power plants.
Let it be the largest. There is no comparison here. We want to reduce air pollution and elimination is not practically possible. This is out of scope as it does not emphasize what happens if incentives are given. However, premise say that it is significant contributor, largest or not does not matter.
(E) The manufacture and the scrapping of cars each generate significant amounts of air pollutants.
If this happens, the aim of lessening the air pollution wont be satisfied as significant amount of air pollution is caused in both old cars as well as manufacturing of new cars and scrapping of old cars. The argument states as premise that
"cars over five years old typically generate significantly greater amounts of pollutants than newer cars". But if the procedure in this transition leads to same amount of pollution, why will people even think of changing their cars even if there are incentives. They are not going to receive the cars for free. These are just incentives. Since government expects that people can help in reducing pollution, they provide incentives. And if new cars are not purchased then there is no point boost in economy.
Answer is E.
Both the aims should be achieved, but here one aim depends on other and hence the primary aim is reducing air pollution as supplemented by the premise. This is the most suitable option.