The correct answer is option 1, Tube feet. Tube feet are the locomotory organs of a starfish. They are small, fluid-filled structures found on the underside of each arm on a starfish. These tube feet are controlled by a series of muscles and can be extended or contracted to help the starfish move and navigate its environment. They work by creating suction on surfaces, allowing the starfish to crawl and cling onto various substrates. They also play a role in capturing prey and manipulating food. Option 2, Paddle, is incorrect as starfish do not have paddles. Option 3, Muscular foot, is incorrect as this term is typically associated with locomotion in mollusks, not starfish. Option 4, Flipper, is incorrect as flipper is a term used to describe the locomotory organs of marine mammals such as dolphins and seals.