The correct answer is option 4. Explanation & Key Takeaways: Graphite: • Graphite is a type of crystal carbon and a half-metal along with being one of the renowned carbon allotropes. • Under the conditions that are ideal, it would be one of the most stable forms of carbon available. • This crystal carbon has a structure that is planar and layered. • Graphene is the term used to denote each layer of the same. Every layer has atoms of carbon arranged in a honeycomb-like network with a division of 0.142 nm with a 0.335 nm distance between planes. Fullerene: • A fullerene is an allotrope of carbon whose molecule consists of carbon atoms connected by single and double bonds so as to form a closed or partially closed mesh, with fused rings of five to seven atoms. • The molecule may be a hollow sphere, ellipsoid, tube, or many other shapes and sizes. • Graphene (isolated atomic layers of graphite), which is a flat mesh of regular hexagonal rings, can be seen as an extreme member of the family. Diamond: • Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. • Diamond has the highest hardness and thermal conductivity of any natural material, properties that are used in major industrial applications such as cutting and polishing tools.