According to paragraph 2, why are dinosaurs popularly said to have "ruled Earth" during the Cretaceous period? A. Dinosaurs were the only species of reptile that existed during the whole of the Cretaceous period. B. Dinosaurs won the battle for food resources over mammals during the Cretaceous period. C. Dinosaurs survived extinction during the Cretaceous period, whereas many other animal species did not. D. Dinosaurs were the physically and ecologically dominant animals during the Cretaceous period.