________ is the purest form of carbon.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the purest form of carbon. This requires knowledge of different allotropes of carbon and their characteristics.

2. **Identifying Allotropes of Carbon**: Carbon exists in several forms, known as allotropes. The most common allotropes include graphite, charcoal, and diamond.

3. **Defining Purest Form**: The term "purest form" implies that the substance consists entirely of carbon atoms without any impurities or other elements.

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