Relationships Among the Animals Having Body Cavities Can Be Easily

Relationships among the animals having body cavities can be easily determined by examination of embryonic development; vertebrates and echinoderms are grouped together because in each group,the

A) infolding that forms the body cavity eventually becomes the anus.
B) zygote divides repeatedly to become a blastula.
C) death of specific cells creates the internal hollow that eventually becomes the body cavity.
D) embryonic coelom is lined with mesodermal tissues.