Biologist: Species with broad geographic ranges probably tend to endure longer than species with narrow ranges. The broader a species' range, the more likely that species is to survive the extinction of populations in a few areas. Therefore, it is likely that the proportion of species with broad ranges tends to gradually increase with time.
The biologist's conclusion follows logically from the above if which of the following is assumed?
A. There are now more species with broad geographic ranges than with narrow geographic ranges.
B. Most species can survive extinctions of populations in a few areas as long as the species' geographic range is not very narrow.
C. If a population of a species in a particular area dies out, that species generally does not repopulate that area.
D. If a characteristic tends to help species endure longer, then the proportion of species with that characteristic tends to gradually increase with time.
E. Any characteristic that makes a species tend to endure longer will make it easier for that species to survive the extinction of populations in a few areas.