The nematodes or roundworms constitute the phylum Nematoda and have a pseudocoelom and complete digestive system. The partial, fluid-filled cavity inside the body of some invertebrates. Cnidarians have two different body plans. Both body plans have radial symmetry. A polyp, such as a hydra, sea anemone, or coral, is shaped something like a vase. Platyhelminthes, a group of soft-bodied, usually much flattened invertebrates and havecavity only one opening to the outside which, in most cnidarians, is surrounded by tentacles for capturing prey. But Porifera does not have a gastrovascular cavity as it does not have specialized tissues and phyla with a true coelom and digestive system. The protostomes include the phyla Mollusca, Annelida, and Arthropoda but not porifera.
So, the correct option is, 'Porifera gastrovascular cavity, mouth from blastopore'.