In parts of the Caribbean, the manatee, an endangered marine mammal, has long been hunted for its meat. Having noted the manatee hunters' expert knowledge of manatees' habits, local conservationists are encouraging the hunters to stop hunting and instead to take tourists on boat rides to see manatees. Tourist interest is high, so the plan has promise of achieving the twin goals of giving the former hunters a good income and helping ensure the manatees' survival.

Which of the following, if true, raises the most serious doubt about the plan's chance of success?

【选项】Many tourists who visit these parts of the Caribbean are uninterested in manatees and would not be willing to pay what the former manatee hunters would have to charge for boat rides to see manatees.