Crops can be traded on the futures market before they are harvested. If a poor corn harvest is predicted, prices of corn futures rise; if a bountiful corn harvest is predicted, prices of corn futures fall. This morning meteorologists are predicting much-needed rain for the corn-growing region starting tomorrow. Ttherefore, since adequate moisture is essential for the current crop' s survival, prices of corn futures will fall sharply today. Which of the following, if true, most weakens the argument above? ['Most people who trade in corn futures rarely take physical possession of the corn they trade.', 'Futures prices for corn have been fluctuating more dramatically this season than last season.', 'Agriculture experts announced today that a disease that has devastated some of the corn crop will spread widely before the end of the growing season.', 'Corn that does not receive adequate moisture during its critical pollination stage will not produce a bountiful harvest.']