The natural source of hydrocarbons is:

Hydrocarbons are organic compounds made up of hydrogen and carbon atoms. They serve as the primary constituents of fuels, lubricants, and many industrial chemicals. The natural source of hydrocarbons is crude oil, a fossil fuel formed over millions of years from the remains of ancient marine plants and animals.

Crude oil is extracted from underground reservoirs and contains a complex mixture of hydrocarbons, including alkanes, cycloalkanes, and aromatic hydrocarbons. These compounds can be separated and refined into products such as petrol, diesel, kerosene, lubricating oils, and petrochemicals. The chemical structure of hydrocarbons determines their physical properties, such as boiling point, viscosity, and flammability.

Other options listed, such as biomass, coal, and carbohydrates, are not primary sources of hydrocarbons. Biomass contains organic matter that can be converted into fuels, but it does not naturally contain hydrocarbon mixtures like crude oil. Coal is primarily carbon-rich but lacks the diversity of hydrocarbon molecules found in petroleum. Carbohydrates, found in plants, consist of carbon, hydrogen, and oxygen, but they are not classified as hydrocarbons because they include oxygen atoms.

The formation of crude oil occurs through geological processes where organic matter is buried under layers of sediment, subjected to high pressure and temperature, and chemically transformed over millions of years. This process produces a dense liquid mixture rich in hydrocarbons that can be extracted and utilized for energy and industrial purposes.

Understanding the natural source of hydrocarbons is important in chemistry and everyday science because it explains the origin of fuels, their chemical composition, and their role in energy production. Crude oil remains the most important and widely used natural source of hydrocarbons worldwide, supporting transportation, manufacturing, and modern life.