I had a tough time choosing between B and C..but ultimately I choose B. Only because the argument mentions insects as the primary reason for the high demand of cotton and the subsequent price increase. Once that is taken away I would imagine that the price of cotton would drop.
But C is attractive also because if the demand remains the same, and the supply increases it would be a logical extension that the price would drop. But I ruled it out because just because there has been no sharp increase in demand over the last few years doesn't mean that there won't be in the years to come.
"No! Try not. Do. Or do not. There is no try.