Over the last thousand years, plant species native to islands have gone extinct at a much faster rate than have those native to mainland regions. Biologists believe that this is because island plants have not adapted the defenses against being eaten by large land mammals that mainland plants have. Ordinarily, populations of large land mammals are not established on islands until after the island is colonized by humans. Which one of the following. if true, most strongly supports the biologist's explanation cited above? ['Large land mammals tend to prefer plants from species native to mainland regions over plants from species native to islands.', 'The rate of extinction of native plant species on an island tends to increase dramatically after human colonization.', 'Many plant species that are not native to islands have become very well established on islands throughout the world.', 'Most of the plant species in the world that have not yet gone extinct are native to mainland regions.']