Science columnist: It is clear why humans have so many diseases in common with cats. Many human diseases are genetically based, and cats are genetically closer to humans than are any other mammals except nonhuman primates. Each of the genes identified so far in cats has an exact counterpart in humans. Which one of the following, if true, most weakens the science columnist's explanation for the claim that humans have so many diseases in common with cats? ['Cats have built up resistance to many of the diseases they have in common with humans.', 'Humans have more genes in common with nonhuman primates than with cats.', 'Cats have more diseases in common with nonhuman primates than with humans.', 'Most diseases that humans have in common with cats have no genetic basis.']