Comparative embryology helped clarify the relationships among major groups of animals while the bilaterians

Coelomates &  Pseudocoelomates

Explanation:

Coelomates: Animals that have a body that incorporates voids are known as coelomates, they have a total body structure, and their bodies are ensured by coelom which goes about as a body skeleton and spares all the interior organs from outer pressure. The coelom is shaped at the stage known as gastrula, after various procedures which incorporate different capacities the mesoderm is isolated into two sections and coelom begins existing between them. The primary layer is near the body itself called endoderm while the other layer is at the external side known as ectoderm.   Pseudocoelomates: Animals that don't have an appropriate body hole are known as pseudocoelomates. This is a direct result of the explanation that they have pseudo coelom which is available between the ectoderm and endoderm and lies outside the mesoderm. They are likewise dissipated and present at more than one spots, thusly, have a structure which doesn't appear to be like different species. In spite of the fact that it is a body cavity and capacities appropriately but since of their temperament, the liquid isn't line appropriately however fills the assemblage of creatures, in light of this the organs are put near one another in a dispersed way and thusly doesn't permit the body to shape a legitimate skeleton.

Your answer is going to be b.