Final answer:
The correct answer is option C, indicating that the farm's marginal cost for fertilizer will increase with the use of new organic fertilizer, as it is more expensive than conventional options.
Step-by-step explanation:
The question revolves around the impact of new fertilizer use on a farm, particularly through the lens of economic concepts such as marginal cost and opportunity cost. Given that organic fertilizers are more expensive than traditional ones, the use of new organic fertilizer would likely increase the marginal cost for fertilizer, as each additional unit of organic fertilizer used is costlier than conventional fertilizer. Consequently, option C is the correct answer since it states that the farm's marginal cost for fertilizer will increase. This is supported by the information provided, which mentions that organic production costs may remain higher than conventional farming due to the cost of organic fertilizers and pest management techniques. Additionally, while the shift towards organic farming increases supply and potentially the equilibrium quantity of organic foods, it is noted that prices may not fall significantly if the increase in demand is comparable to the increase in supply, indicating that the marginal revenue might not compensate for the increased marginal cost.