Correct Option: D  [ Methane ]
Remark:
Methane (CH₄) is not an allotrope of carbon. It is a chemical compound made up of one carbon atom and four hydrogen atoms. In contrast, allotropes are different structural forms of the same element in the same physical state. Carbon has several allotropes, including diamond, graphite, and fullerene (C-60), which differ in atomic arrangement and physical properties.
Other options (for context)
- Diamond: An allotrope of carbon where each carbon atom is tetrahedrally bonded to four others, making it extremely hard.
- Graphite: An allotrope of carbon with layers of hexagonally arranged atoms; good conductor of electricity.
- C-60 (Fullerene): A spherical allotrope of carbon consisting of 60 atoms arranged like a soccer ball.