A major impediment to wide acceptance of electric vehicles even on the part of people who use their cars almost exclusively for commuting is the inability to use electric vehicles for occasional extended trips. In an attempt to make purchasing electric vehicles more attractive to commuters, one electric vehicle producer is planning to offer customers three days free rental of a conventional car for every 1,000 miles that they drive their electric vehicle.

Situation - Limited acceptance of electric vehicles even on the part of people who use their cars almost exclusively for commuting.
Impediment - The inability to use electric vehicles for occasional extended trips
Proposed plan - To offer customers three days free rental of a conventional car for every 1,000 miles that they drive their electric vehicle.
Q : Plan is NOT good.

Which of the following, if true, most threatens the plan's prospects for success?

(A) Many eclectic vehicles that are used for commercial purposes are not needed for extended trips.
We are concerned about commuters in general not with those who will be using eclectic vehicles only for commercial purposes. What about those who are using eclectic vehicles for other usages? : They [i]may be needing these vehicles for occasional long/extended trips [/i]

Also, as the argument itself lays emphasis on the fact - major impediment to wide acceptance of electric vehicles even on the part of people who use their cars almost exclusively for commuting is the inability to use electric vehicles for occasional extended trips. This option is irrelevant.

(B) Because a majority of commuters drive at least 100 miles a week, the cost to the producer of making good the offer would add considerably to the already high price of electric vehicles.

The cost to the producer of making good the offer --> would add considerably to the already high price of electric vehicles.[/b]

This option means that the already high prices of the electric vehicles will increase considerably. That is, the customers will have to spent a significant amount of bucks for buying these vehicles. So, instead of the proposed offer, the considerable high price will then be the impediment to the wide acceptance of these vehicles. Therefore, correct answer.

(C) The relatively long time it takes to recharge the battery of an electric vehicle can easily be fitted into the regular patterns of car use characteristic of commuters.
so what?? if that is true? This option slightly strengthens the plan. So, incorrect.

(D) Although eclectic vehicles are essentially emission-free in actual use, generating the electricity necessary for charging an electric vehicle's battery can burden the environment.
Damage/Burden to environment is out of scope for the problem in hand. How does it prove that the plan is bad??

(E) Some family vehicles are used primarily not for commuting but for making short local trips, such as to do errands.
Some = Atleast One. So, if some people are using vehicles for short local trips that really does not matter. The primary purpose of the trip is totally out of context.

If anything, the vehicles are used for the short local trips then plan will be successful, if we think deep.