Coral are:

Coral are:

• A. A single-celled organism
• B. A fish
• C. A sponge
• D. Marine invertebrates that form colonies and build reefs, consisting of many individual polyps

Answer: (D)

Coral are marine invertebrates that form colonies and build reefs, consisting of many individual polyps. Each polyp is a small, soft-bodied animal that lives together with others; over time they secrete calcium carbonate skeletons that interlock to create the hard framework of a reef. This colonial lifestyle means a reef is built by many individual polyps working as a community. They’re not single-celled organisms, not fish, and not sponges. In many corals, photosynthetic algae live inside the coral tissues and provide energy, aiding reef growth in sunlit shallow waters. This combination of living colonies that construct calcium carbonate structures is what defines corals.