The crystalline forms of carbon are diamond, graphite and______.

• A. Coal
• B. Coke
• C. Charcoal
• D. Fullerene

The crystalline forms of carbon include several distinct structures, each with unique properties. Among the options provided, the correct answer is D. Fullerene.

Understanding Carbon Structures

Carbon can exist in various forms, known as allotropes. Here are some key examples:

• Diamond: A hard, transparent form used in jewelry and cutting tools.
• Graphite: A soft, black form used in pencils and as a lubricant.
• Fullerene: A molecular form of carbon that can resemble hollow spheres or tubes.

While coal, coke, and charcoal are carbon-rich materials, they do not have a crystalline structure like diamond, graphite, or fullerene. Thus, fullerene is the correct answer to complete the list of crystalline forms of carbon.