_______ and _______ are the two crystalline forms of carbon.

Explanation

To answer the question about the two crystalline forms of carbon, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for the two crystalline forms of carbon. Crystalline forms refer to the solid structures that have a defined geometric shape and arrangement of atoms.

2. **Identify Crystalline Forms of Carbon**: There are several allotropes of carbon, but we need to focus on the crystalline forms specifically. The two most well-known crystalline forms of carbon are:
- **Graphite**
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