Question: Fact 1: Many corals secrete an exoskeleton that builds up to become a coral reef.  Fact 2: An insect has a hard outer covering called an exoskeleton.  Given the two facts above, answer the question "Many corals secrete what to form a coral reef?" with the following options:  - Chlorophyll  - salt and water.  - The area was once underwater  - Chemical energy  - aqueous solution  - Organic compounds  - gastropod shells  - hard outer covering
Answer:
hard outer covering