A coral stone is made of

Options

A. Several corallites
B. Corallium
C. A single corallite
D. Both A and B.

Answer

To answer the question "A coral stone is made of," we can break down the information as follows:

### Step-by-Step Solution:

1. **Understanding Coral Structure**: Coral stones are formed by the accumulation of skeletal structures produced by coral polyps. Each polyp secretes a calcium carbonate skeleton.

2. **Identifying Corallites**: The individual skeletal cups produced by each coral polyp are called corallites. Each polyp resides within its own corallite, which provides support and protection.

3. **Formation of Coral Stone**: When many corallites from multiple coral polyps come together, they form a larger structure known as a coral colony. Over time, these colonies contribute to the formation of coral stones.

4. **Conclusion**: Therefore, a coral stone is made up of several corallites, and it can also be described as being made up of a single corallium (the collective term for the coral colony).

5. **Final Answer**: The correct answer is that a coral stone is made of both several corallites and a single corallium.

### Final Answer: Both A and B (Option 4)

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