Which of the following, if true, most weakens the argument? A. When grapes are grown in greenhouses, it is relatively easy to control the grape pests that thrive in air enriched with carbon dioxide. B. Recent improvements in pest control have increased grape yields in many vineyards. C. Increasing carbon dioxide levels in greenhouses has not been shown to improve the quality of grapes grown in greenhouses. D. Increasing carbon dioxide levels in greenhouses increases the sweetness of raisins made from grapes grown in the greenhouses. E. As the carbon dioxide level in the open air increases, temperatures at the Earth's surface will also increase.