Final answer:
Sea stars (A), also known as starfish, have tube feet and arms that extend from a middle body used for movement and feeding. Brittle stars, sea urchins, and sea cucumbers also have tube feet but either lack the characteristic arms or utilize them differently.
Step-by-step explanation:
The animals that have tube feet and arms that extend out from a middle body are sea stars (A), also known as starfish. Sea stars belong to the class Asteroidea and are distinguished by their thick arms that extend from a central disk. These arms contain organs such as digestive glands, gonads, and, notably, the tube feet which are unique to echinoderms like sea stars. On the underside of sea stars, tube feet are arranged in rows along each arm and are part of the water vascular system. This system allows for movement by expanding and contracting chambers within it, which force seawater into the tube feet, extending or retracting them appropriately for locomotion.
Brittle stars (D), belonging to class Ophiuroidea, differ in that they have long, thin, flexible arms that do not contain organs and use a different method for movement. Sea urchins and sand dollars (B) lack arms altogether and have tube feet for slow movement and feeding, while sea cucumbers (C) are soft-bodied with rows of tube feet but do not possess the extending arms characteristic of sea stars.