Which of the following is a solid hydrocarbon?

Paraffin wax is classified as a solid hydrocarbon because it mainly consists of straight-chain hydrocarbons that are derived from petroleum. These long-chain alkanes typically have melting points that allow them to remain in a solid state at room temperature. When considering its composition, paraffin wax is non-polar and has a waxy texture, characteristic of solid hydrocarbons.

Other options present different characteristics. Petrolatum, while also a petroleum derivative, is more of a semi-solid and has a broader range of consistency depending on its formulation. Mineral oil consists mostly of liquid hydrocarbons, making it unsuitable as a solid hydrocarbon. Stearic acid, although a fatty acid with a long hydrocarbon tail, is categorized differently due to its nature as an acid rather than a hydrocarbon solid strictly classified under alkanes or similar structures. Thus, the distinct properties and structure of paraffin wax solidify its classification as a solid hydrocarbon.