Which of the following best describes a hydrocarbon?

A hydrocarbon is defined as an organic compound that consists entirely of hydrogen and carbon atoms. This definition is fundamental in organic chemistry and highlights the simplicity and basic structure of hydrocarbons, which can exist in various forms such as alkanes, alkenes, and alkynes.

Hydrocarbons can be saturated, with single bonds between carbon atoms, or unsaturated, containing double or triple bonds. Because they only contain hydrogen and carbon, hydrocarbons serve as a building block for many other organic compounds and are significant in chemistry, particularly in the context of fuels and raw materials in the petrochemical industry.

The other options describe different types of compounds that do not fit the definition of hydrocarbons. For instance, the first option mentions carbon and nitrogen, which is characteristic of different classes of compounds like amines or nitriles, thus excluding them from being categorized as hydrocarbons. The second option involves hydrogen and oxygen, pointing towards compounds such as water or alcohols, but they do not meet the hydrocarbon requirement of containing only carbon and hydrogen. Lastly, the fourth option includes sulfur along with carbon, which is again outside the hydrocarbon classification, as hydrocarbons do not contain elements other than hydrogen and carbon.