Answer:
Earthworm - have a coelom and a closed circulatory system.
Scallops or clams - has a mantle and an open circulatory system.
Starfish - has an endoskeleton made of calcium-rich plates.
Spider - exhibits the phenomenon of molting.
Explanation:
Earthworm belongs to Phylum Annelida. They are metamerically segmented, triploblastic and bilaterally symmetrical. They have a closed circulatory system and a coelom (true body cavity).
Scallops or clams belong to Phylum Mollusca, the second largest animal phylum. They are coelomate, triploblastic, bilaterally symmetrical organisms having an open circulatory system. They have a calcareous shell covered body with a distinct head, muscular foot, visceral hump and a mantle (soft and spongy layer of skin) over the hump.
Starfish belongs to Phylum Echinodermata, which consists of exclusively free-living marine organisms. They have an endoskeleton made up of calcium carbonate structures. They are coelomate, triploblastic and have a water vascular system that is used for respiration, locomotion, food capture and transport.
Spiders belong to Phylum Arthropoda. They have chitinous covered segmented bodies, jointed legs and exoskeletons (hard external shells). Arthropods periodically shed their exoskeletons or shells in order to grow, this process is called molting. They are coelomate, triploblastic, bilaterally symmetrical organisms having an open circulatory system.
