Of the total precipitation that the city of Tinyland receives, the proportion of rain has decreased by three percentage points over the past ten years. Since sugarcane is a rain-dependent cash crop of Tinyland, these declines are likely to have a noticeably negative economic impact on the sugar and ethanol business, a staple of the economy of Tinyland.
Which of the following, if true, most seriously weakens the argument given?The argument is: the share of precipitation that is rain is down by 3 percentage points, sugarcane depends on rain, so the sugar and ethanol business will be hurt. The best weakener shows that despite the smaller share of rain, the actual water available to crops (or actual rainfall amount) has not decreased, so the economic impact is unlikely to be negative.
A. The clouds that cause rain over Tinyland are formed more frequently now than in the past ten years.
More cloud formation does not necessarily mean more usable rainfall, and it does not directly address whether rainfall (or water for sugarcane) is down. Weak.
B. Rain has become more evenly distributed over the past ten years.
More even distribution could actually help farming, but it does not clearly show that the total rain amount is not down. It is a possible weakener, but not the strongest.
C. The change in weather conditions has led to more snow and hail in Tinyland than rain in the past decade.
This supports the premise that rain is a smaller share; it does not weaken the predicted negative impact.
D. The level of precipitation has registered a significant increase over the past ten years.
This is the strongest weakener. The argument only talks about the proportion of rain, not the total amount of precipitation. If total precipitation rose a lot, then the amount of rain could be the same or even higher despite a slightly smaller percentage, so the claim of a likely negative impact becomes much less credible.
It breaks the key link between “lower share of rain” and “less rain available for sugarcane.”E. Tinyland has recently mandated using ethanol as a necessary additive to automotive fuel.
This would tend to increase demand for ethanol, which could offset economic harm, but it does not address whether sugarcane production will actually suffer from less rain. Not the most direct weakener.
Answer: (D)