Main point questions require us to identify the conclusion. Let's look at the argument:
People say EVs are a solution to the air pollution problem. EVs require charging and most electricity is generated by fossil fuel plants. Increasing the number of EVs would require more generating capacity. Even if all conventional cars are replaced by EV _________________________________________________________ It is an exchange of one source of fossil fuel pollution for another.
The main conclusion here is that electric vehicles merely result in switching from vehicle-emissions to electric generation plant emissions and are not a viable solution to the air pollution problem. (D) accurately summarizes this conclusion and is the thus, the correct answer choice.
(C) says "all forms of automobile transportation are equally harmful to the environment in terms of the air pollution they produce."
This is incorrect for two reasons: (1) the argument is only about EVs vs gasoline-powered, not any other types of transportation, e.g. hybrid vehicles; (2) the author never says they are equally harmful, only that there are emissions associated with EVs as well. It is possible that emissions from generation plants that are usually located further from urban areas are less harmful, for instance. He never actually attempts to compare the extent of vehicle emissions with power plant emissions but merely concludes that EVs are not a complete solution to the air pollution problem.
