The correct answer is A. Dead animals.
Here's why:
1. Coral reefs are primarily made up of the skeletons of tiny marine animals called coral polyps.
2. These coral polyps extract calcium carbonate from seawater to build protective skeletons around themselves, forming intricate structures over time.
3. When the coral polyps die, their hard skeletons remain and new polyps build upon them, creating the structure of a coral reef.
4. So, in essence, coral reefs are composed of the accumulated skeletons of countless generations of coral polyps.
Remember, coral reefs are diverse and vibrant ecosystems that provide habitats for a wide range of marine life. Understanding what they are made of helps us appreciate the delicate balance and importance of these underwater ecosystems.
