The purest and the densest variety of carbon is ..........

Explanation

To solve the question "The purest and the densest variety of carbon is ..........", we can follow these steps:

### Step 1: Understand Carbon Allotropes
Carbon exists in several allotropes, which are different structural forms of the same element. The most common allotropes of carbon include diamond, graphite, fullerenes, and graphene.

**Hint:** Research the different allotropes of carbon and their properties.

### Step 2: Identify the Characteristics of Diamond
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