Mammal Numbers, Diversity, and Size Increased Dramatically at the End

Mammal numbers, diversity, and size increased dramatically at the end of the Cretaceous because

A) non-avian dinosaurs became extinct at that time.
B) mammals evolved differentiated teeth that allowed them to outcompete non-avian dinosaurs.
C) mammals were a group of theropods similar to the group that led to modern birds.
D) mammals were viviparous, leading to greater reproductive success than in the dinosaurs.
E) mammals evolved hollow bones, allowing them to escape from predatory dinosaurs.