单选题
When the Pinecrest Animal Shelter, a charitable organization, was in danger of closing because it could not pay for important repairs, its directors appealed to the townspeople to donate money that would be earmarked to pay for those repairs. Since more funds were ultimately donated than were used for the repairs, the directors plan to donate the surplus funds to other animal shelters. But before doing so, the directors should obtain permission from those who made the donations.
Which one of the following principles, if valid, most Helps to justify the position advocated above and yet places the least restriction on the allocation of funds by directors of charitable organizations?