Paragraph 9 suggests all of the following possible explanations for the uniqueness of the Cambrian explosion EXCEPT A. the inability of later animals to evolve body plans different from those that appeared during the Cambrian period B. the post-Cambrian appearance of efficient predators occupying nearly every environmental niche C. the decline in the number of habitats having sufficient resources to support the rapid evolution of new species D. the limited range of genetically possible body types