You are presented with the question "How are atolls built?" and the following answer choices: - important habitats - By coral exoskeletons - by fish - with machines - by a type of eel - It used to be covered by water - The area was once underwater - reusing materials Now knowing that many corals secrete an exoskeleton that builds up to become a coral reef and an atoll is the third type of reef, choose the best answer.
Answer:
By coral exoskeletons