Greenville, an agricultural city, will be doubling its cattle

the proposal is this — reduce greenhouse gases to improve cattle rearing by using solar vehicles instead of gasoline powered ones.

If gasoline powered vehicles do not emit greenhouse gases, then the proposal will fall apart — no reduction in green house gases will be achieved.

(I think this problem is terrible; the logic employed does not make sense either. Ignore this one)

D is also questioning the feasibility of the plan.
If Vehicle pollution is not a cause for green house emission then the plan will not work.As the plan is based on this assumption itself.

E is the right answer.

GMATNinja, gmat1393, GMATNinjaTwo, nightblade354 i believe the OA is wrong,

Option D also weakens the proposal,

Only E does not weaken it.

Please help

In a closer look, option D makes sense. The proposal is that "To make the city more conducive for cattle rearing, Greensville’s mayor plans to reduce the amount of greenhouse gasses generated in the city. The mayor also argues that solar power represents a far greener source of energy (producing lesser greenhouse gasses) than does fossil fuel. Hence, even if vehicle emissions are not causative for the production of greenhouse gasses, the mayor's plan to reduce greenhouse gasses will not be affected anyway because solar-powered vehicles emit far less greenhouse gasses than do gasoline-powered vehicles.

nightblade354 your take please

I take issue with this question. If a question is an "other source" and has a less than 20% correct rate, we must come to the conclusion that it is probably a bad question. I can make a logical argument as to why a few of these are completely irrelevant. An un-GMAT like question and should be avoided in my opinion.

please explain in brief all the options

Greenville, an agricultural city, will be doubling its cattle population the coming year. To make the city more conducive for cattle rearing, Greensville’s mayor plans to reduce the amount of greenhouse gasses generated in the city. He plans to promote widespread use of solar powered vehicles rather than gasoline powered ones; he therefore plans to ban gasoline sale for use in vehicles. He argues that solar power represents a far greener source of energy (producing lesser greenhouse gasses) than does fossil fuel.

Argument: The proposed plan will lead to less greenhouse gases, thereby facilitating the cattle rearing. We need to find an option which does not weaken or at least attack this argument.

All of the following call into question the feasibility of the proposed plan, EXCEPT

A The process of making solar cells that will power vehicles involves the use of more fossil fuel than what it would take to power a conventional gasoline vehicle through its entire life cycle- Weakener
B Since most of the citizens of Greensville prefer gasoline powered vehicles, they will drive to their neighboring cities to fuel up, when they need to- Weakener
C It has been found that the amount of greenhouse gasses produced by cattle far exceeds that of those produced by gasoline powered vehicles- The proposed plan will hence wont add much if the quantity of greenhouse gases add much to the current levels
D New research has shown evidence that disproves the popular notion that vehicle emissions are causative for the production of greenhouse gases.- Since vehicle emissions are not causing production of greenhouse gases, the plan will be feasible even if solar cells are deployed in them. You can say that current levels of emissions add much to it, thereby making the plan seem bad but the argument to decrease greenhouse gases remains unaffected by this option.
E There was a decrease of 20 percent in the production of solar cells last year- We are not talking about supply demand constraint hence this would make the plan difficult to manage the ban of gasoline.