单选题
Researchers have discovered a new poison, bromethalin, that is lethal to all rats, even to those species that have become immune to other poisons, as well as to those rats that eat only the most minute quantities. Tests have demonstrated that rats will not learn to avoid bromethalin and that carcasses of rats killed by bromethalin pose no threat to the well-being of other animals. Which of the following statements, if true, would support the researchers' claim that carcasses of rats killed by bromethalin will not pose a threat to other animals?