What is the main characteristic of hydrocarbons found in crude oil?

Hydrocarbons, which are the primary components of crude oil, are characterized by their chemical composition consisting solely of carbon and hydrogen atoms. This characteristic is fundamental to hydrocarbons, distinguishing them from other organic compounds that may contain different elements such as oxygen, nitrogen or sulfur.

This composition leads to varied structural forms, including alkanes, alkenes, and alkynes, and can greatly influence their physical properties and behavior. Hydrocarbons in crude oil range in size from small molecules (like methane) to large complex structures (like those found in heavy oils), but the essential feature remains that they exclusively contain carbon and hydrogen.

The other options do not describe the main characteristic of hydrocarbons accurately. For instance, hydrocarbons can vary in state; some are gases, while others are liquids or solids at room temperature, so they are not all gases. Additionally, hydrocarbons are generally non-polar molecules because they lack significant electronegative atoms, and they tend to be insoluble in water due to their hydrophobic nature. Therefore, the defining feature of hydrocarbons in crude oil is that they consist only of carbon and hydrogen.