The answer is:
Five
Sea stars do not rely on a jointed, movable skeleton for support and locomotion but instead possess a hydraulic water vascular system that aids in locomotion.
Sea stars usually hunt for shelled animals such as oysters and clams. They have two stomachs. One stomach is used for digestion, and the second stomach can be extended outward to engulf and digest prey. This feature allows the sea star to hunt prey that is much larger than its mouth would otherwise allow. Sea stars are able to regenerate lost arms. A new sea star may be regenerated from a single arm attached to a portion of the central disk.