Hint: It's a mechanism employed by echinoderms, like sea stars and sea urchins, for locomotion, food and waste transportation, and respiration. The system consists of canals connecting numerous tube feet. Echinoderms move by on the other hand contracting muscles that power water into the cylinder feet, making them increment and push against the base, at that point unwinding to allow the feet to withdraw.
A) Stone canal may be a calcareous tube that connects the madreporite to the ring canal.
B) The madreporite is the plate with millions of perforations that controls the entry of seawater into the vascular system.
C) The ring waterway is a round ring and is arranged around the mouth and offers to ascend to provide for expansions called a radial canal.
D) Ossicles are small calcareous elements embedded within the dermis that give rigidity and protection.
Additional information: In sea stars, water enters the system through a sieve-like structure on the side of the animal, called the madreporite. This overlies a little sac, or ampulla, associated with a conduit named the stone canal, which is, as its name suggests, regularly fixed with calcareous material. The stone trench races to a roundabout ring waterway, from which outspread channels run outwards along with the ambulacral grooves. Each arm consists of a groove on its underside of a starfish, while, in sea urchins, they line the surface of the body.
Each side of the outspread trenches offers to ascend to a column of bulb-like ampullae, which are associated by means of a lateral canal.
In sea stars, these are always staggered, in order that an ampulla on the left follows one on the proper, then on down the length of the radial canal. The ampullae are connected to suckerlike podia. The entire structure is called a tube foot.
So the correct answer is ‘(b) Madreporite’.
Note: In most cases, the tube feet are present in two rows and are arranged in such a way by connecting the equal lengths small lateral canals and ampullae to the radial canal. In some species, however, there are alternately long and short lateral canals, giving the looks of two rows on all sides of the groove, for four in total.