Which amongst the following is not free state of carbon?

Options

A. Graphite
B. Diamond
C. Fullerene
D. Petrol

Explanation

To determine which option is not a free state of carbon, we first need to understand what is meant by "free state of carbon." The free states of carbon refer to its allotropes, which are different structural forms of carbon that exist in nature. The most common allotropes of carbon include:

1. **Diamond** - A crystalline form of carbon where each carbon atom is tetrahedrally bonded to four other carbon atoms.
2. **Graphite** - A layered structure where carbon atoms are bonded in sheets, allowing them to slide over one another.
3. **Fullerenes** - Molecules composed entirely of carbon, taking the form of hollow spheres, ellipsoids, or tubes.

Now, we analyze the given options. The question asks which of the following is not a free state of carbon. The options include:

- **Graphite**
- **Diamond**
- **Fullerene**
- **Petrol**

From our understanding, graphite, diamond, and fullerenes are all allotropes of carbon and thus are considered free states of carbon. However, petrol is a complex mixture of hydrocarbons and does not consist solely of carbon in its free state.

### Step-by-Step Solution:
1. **Identify the allotropes of carbon**: Recognize that diamond, graphite, and fullerenes are the allotropes of carbon.
2. **Analyze the options**: Check each option to see if it is a pure form of carbon.
- **Graphite**: Allotrope of carbon.
- **Diamond**: Allotrope of carbon.
- **Fullerene**: Allotrope of carbon.
- **Petrol**: A mixture of hydrocarbons, not a pure form of carbon.
3. **Conclusion**: Since petrol is not a pure form of carbon and does not represent a free state of carbon, it is the correct answer.

### Final Answer:
The option that is not a free state of carbon is **Petrol (Option D)**.