Farmer: Agricultural techniques such as crop rotation

I am no expert, still let me give it a shot. Do let me know in case you have any further doubts.

Farmer: Agricultural techniques such as crop rotation that do not use commercial products may solve agricultural problems at least as well as any technique, such as pesticide application, that does use such products. Nonetheless, no private for-profit corporation will sponsor research that is unlikely to lead to marketable products. Thus, for the most part, only government-sponsored research investigates agricultural techniques that do not use commercial products.

Which one of the following, if true, most strengthens the farmer's argument?

(A) The government sponsors at least some investigations of agricultural techniques that are considered likely to solve agricultural problems and do not use commercial products. -It is restating the fact given in the premise, that mostly only government sponsored research investigates agricultural techniques that do not use commercial products. This doesn't strengthen the argument.

(B) For almost any agricultural problem, there is at least one agricultural technique that does not use commercial products but that would solve that agricultural problem. -OK, this might be true. Our argument doesn't bother about such a fact. It is out of scope.

(C) Investigations of agricultural techniques are rarely sponsored by individuals or by any entity other than private for-profit corporations or the government. -Looks good lets park it aside for now. Since mostly investigation of agricultural techniques is sponsored by government and as per the stated fact we know that profit making firms don't support such researches, this eliminates any individual's interest in the research.
Lets try to negate this statement and see its impact on the argument. Since this option should strengthen the argument, the negation should weaken the argument.
Negation: Investigations of agricultural techniques are rarelyMOSTLY sponsored by individuals or by any entity other than private for-profit corporations or the government -This directly attacks our argument's assumption that MOSTLY ONLY GOVERNMENT SUPPORTS SUCH RESEARCHES.
Thus, this option validly strengthens the argument

(D) Most if not all investigations of agricultural techniques that use commercial products are sponsored by private for-profit corporations. -We are worried about the agricultural researches that do not use commercial products. Out of scope

(E) Most if not all government-sponsored agricultural research investigates agricultural techniques that do not use commercial products. -This is again only restating what's given in the argument. This doesn't strengthen the argument in any way.
Lets try negation here again.
Negation: Most if not all government-sponsored agricultural researches DO NOT investigates agricultural techniques that do not use commercial products -This statement states that not all government funded researches use commercial products. This might be true, because from the argument we know that mostly only government funds agricultural researches. Since only government funds researches it doesn't mean that all the researches of government are pertaining to the particular type of research. The government might also be researching simultaneously on other things as well. So this point doesn't effect our argument at all.

Always remember, the premise if restated in the options NEVER strengthens the argument.

Hope it helps!

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