Which of the following is the main point of Karen's reply to David? A. Although it would be desirable to preserve all endangered species, doing so is not economically feasible. B. Even if the value to humanity of a given species is known, that value should not be a factor in any decision on whether to expend effort to preserve that species. C. Species whose contributions to humanity are direct should have a higher priority for preservation efforts than species whose contributions to humanity are only indirect. D. Since the methods for deciding which species have the most value to humanity are imperfect, informed decisions cannot be made on the basis of the assessment of such value. E. The preservation of endangered species whose value to humanity can be reliably predicted is more important than the preservation of species whose value for humanity is unpredictable.