Antiwhaling activist: Not all species of whales are threatened with extinction. Nevertheless, given the highly mechanized technology used in whaling, a ban on the whaling of endangered species cannot be enforced without banning the whaling of all other species. Hence, since hunting endangered whale species should be banned, all whale-hunting should be banned. Which one of the following principles, if established, would do the most to justify the conclusion drawn by the antiwhaling activist? ['If a certain activity ought to be prohibited, so should any other activity that interferes with the enforcement of that prohibition.', 'If a commercial form of a certain activity ought to be prohibited, then so should all noncommercial forms of that activity.', 'The fishing industry has a right to hunt members of species that are not endangered.', 'All actions that are instrumental in achieving ends that are permissible are themselves permissible.']