Hardin argued that grazing land held in common (that is, open to any user) would always be used less carefully than private grazing land. Each rancher would be tempted to overuse common land because the benefits would accrue to the individual, while the costs of reduced land quality that result from overuse would be spread among all users. But a study comparing 217 million acres of common grazing land with 433 million acres of private grazing land showed that the common land was in better condition. The answer to which of the following questions would be most useful in evaluating the significance, in relation to Hardin's claim, of the study described above? (A) Did any of the ranchers whose land was studied use both common and private land? (B) Did the ranchers whose land was studied tend to prefer using common land over using private land for grazing? (C) Was the private land that was studied of comparable quality to the common land before either was used for grazing? (D) Were the users of the common land that was studied at least as prosperous as the users of the private land? (E) Were there any owners of herds who used only common land, and no private land, for grazing? 首先，这道题目应该如何去理解？其次，对于这个答案我也觉得百思不得其解，希望nn们能解释一下，谢谢：） | 
