Chemical fertilizers and pesticides are very expensive

Please provide the OA. Thank you!
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I understand that this could be a solution from my personal perspective - but the OA doesn't have anything to do with relating cost.
Can you please explain why this is the correct answer? Because who cares if the quality goes up or down as long as the price*units sold is a net positive with manure?

Hey there!
As per the Author's reasoning, Since Chemical fertilizers and pesticides are very expensive, farmers should use Natural Manure because it is relatively cheaper in order to increase their profits.
Now you think if Natural Manure in any way effects the quality of the crops, than farmers won't be able to increase their profits, and hence switching to Natural Manure (only to save the cost) would defeat the ultimate the goal of the farmers i.e. to increase the profits.
Hence the author assumes that switching to Natural Manures won't effect the quality of the crops and this is what is being mentioned in Option choice (D)
Now if you negate choice D, see how the author's conclusion gets shattered. So its the true assumption.
Hope it's clear now!

Even if the quality of the crops is bad, there is a possibility that there exists a profitable market for it. But if chemical fertilisers forms a significant portion of the cost of production that directly impacts my profit. Hence the answer should be E.

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I understand the reasoning, but all of the answers are pretty crappy. This answer is probably the best out of all of them, but I didn't select it based on the logic i stated above. This answer also assumes that the price is fixed and that only a particular quality of crop will sell. Maybe there is a market for cheaper, lower quality vegies?

You could also argue E because it assumes that changing the fertilizer is the best way to increase profits, rather than some other method - but that requires more assumptions than provided in the question.
Where did you get this question from?

Conclusion: Farmers, who wish for profit, must use natural manure.
Premise 1: Chemical fertilizers and pesticides are expensive and will increase the costs of production.
Premise 2: Natural manure is relatively cheaper

A- Had the option been yield per unit of land does not suffer, then this would have been right. Eliminate A.
B- Availability doesn't matter here. Eliminate B.
C- Negating this does not affect the conclusion Eliminate C.
D- Quality of crop remains the same despite the change. Essentially, this option says that the change does not affect the product (crop). Negating this would nullify the conclusion. So Hold On.
E- Cost of fertilizers form sizeable part of cost of production. Negating this, we will get "Cost of fertilizers does not form sizable part of cost of production". Assume this to be true. Now, the premise 2 says, compared to fertilizers, natural manure is relatively cheaper. Let us assume this,
Production cost excluding Fertilizer - 100 $
Cost of Fertilizer - 1 $
Cost of Natural Manure - 0.5$
Now, to wish for profit, a farmer, who wishes for profit, would still go with Natural manure, irrespective of the cost associated with fertilizers. So, irrespective of their effect on the production cost, fertilizers are least desirable. Even with the negation, the conclusion holds true.
Option D is the correct choice.

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