Which one of the following types of compounds always includes carbon, hydrogen, and oxygen?

Carbohydrates are organic compounds that are characterized by their consistent composition of carbon, hydrogen, and oxygen. The general formula for carbohydrates is often represented as Cn(H2O)n, indicating that for every carbon atom, there are typically two hydrogen atoms and one oxygen atom. This specific combination of these three elements is fundamental to the structure and function of carbohydrates, which serve as a primary energy source for living organisms.

In the context of the other choices, proteins are made up of amino acids that contain carbon, hydrogen, oxygen, and nitrogen, but they do not have a consistent ratio of these elements like carbohydrates do. Vitamins are diverse organic compounds and may contain various elements, but they do not universally include only carbon, hydrogen, and oxygen. Minerals, on the other hand, are inorganic substances that do not contain carbon at all. Hence, carbohydrates emerge as the unique category that consistently includes only carbon, hydrogen, and oxygen in their structure.