If an increase in dicynodont species diversity (in other words, number of species)occurred soon after the Permian extinction, and if it occurred for the same general reason usually given for the increase in mammalian diversity following the Cretaceous extinction, then it should be attributed to
A) an innovation among the dicynodonts that allowed them to fill brand-new niches. B) the availability of previously occupied niches. C) the extinction of the dinosaurs (except the birds). D) their outcompetition of many other terrestrial organisms.