Answer: 3.Roundworm
Explanation:
Pseudocoelomate animals which have a fluid filled body cavity. The tissues in these organisms are derived from the mesoderm. These organisms lack a circulatory system, lack a endothelial lining of a coelom. The hydrostatic pressure build inside the fluid body cavity is responsible for giving a body supportive framework that gives a skeletonic structure to the animal. Example of these organisms includes the nematodes or roundworms.
