Bunuel
If the city goes on polluting the air at present rates, air quality and visibility over the city will begin to suffer, rainwater may be polluted, and the city will contribute to the global problem of greenhouse emissions. Taxing every polluting commercial establishment per volume of polluted air or per particulate volume of greenhouse emissions will induce businesses to reduce the amount of pollution they emit; this charge will therefore protect the city's air.
Which of the following is an assumption made in drawing the conclusion above?
A. Businesses will reduce the amount of pollution they emit by reducing the number of products they build.
B. The tax will not significantly affect the commercial health of most businesses, even if their factories do not reduce the amount of pollution they emit.
C. The tax will not induce businesses to dispose of their greenhouse gas pollution covertly.
D. The quality of the air is an important issue for most of the city's residents.
E. Polluted air could be purified and cleaned of greenhouse gasses through technology installed at company factories at the point of emission.
OFFICIAL EXPLANATION:
Reading the question: the prompt concerns a plan, and we need to find an assumption in the plan. Plans tend to have lots of assumptions, but they can be difficult to think of. We tax polluters, so they pollute less--no assumption jumps out. Without a specific prediction, therefore, we can apply a basic filter to each answer choice: does it have any relevance to whether the plan will work?
Applying the filter: We test the choices for relevance to the plan. In choice (A), reducing pollution is part of our conclusion, but the "number of products" need not be part of it. Choice (B) is not critical to the argument; it doesn't say or claim or require that businesses will like the tax or even survive it. Choice (C) looks relevant. Choice (D) is irrelevant to whether the tax will work. And choice (E) is not required for the plan to work, as we can see by a negation test: say there isn't a way to purify gasses at the point of emission. They could still pollute less, by producing less, or by capturing the air and shipping it into space in sealed containers, or whatever. So choice (E) is out.
Logical proof: We're left with (C), so we apply the negation test. Negating it, we get, "The tax will induce businesses to dispose of their greenhouse gas pollution covertly." That statement, if true, deals a severe blow to the argument. The plan won't achieve its aim if polluters continue to pollute covertly. Choice (C) is indeed critical.
The correct answer is (C).