Correct Option: D

Coelom is a fluid filled space between body wall and alimentary canal which is lined by mesoderm on both sides. Coelenteron is the sac like body cavity in coelenterates. Blastocoel is the fluid filled cavity of blastocyst. Archenteron is the gut cavity in the gastrula enclosed by the endoderm. The open and of it is called blastopore.