The correct option is A Mollusca- Pseudocoel
In molluscs, the body cavity is true coelom called eucoelom. It is greatly reduced and is represented by cavities in the pericardium, kidneys, and gonads. Spaces among the viscera contain blood and are called hemocoel. Nematocysts are the stinging cells present in coelenterates which inject toxins to paralyze the prey. Chloragogen cells are excretory cells present in annelids such as the earthworm. They take up excretory matter from the blood capillaries of the gut and from the coelomic fluid of coelom. The excretory matter is then passed outside through dorsal pores. In echinoderms, a part of larval coelom is modified into water-filled ambulacral or water vascular system with tube feet to help in locomotion. Thus, the correct answer is option A.