Which of the following elements are always present in carbohydrates?

In carbohydrates, the essential elements that are always present are carbon (C), hydrogen (H), and oxygen (O). Carbohydrates are organic compounds that consist primarily of these three elements, which can be represented by the general formula ( C_n(H_2O)_n ).

The presence of carbon is fundamental because it serves as the backbone of the structure. Hydrogen atoms are attached to the carbon atoms, and oxygen is typically present in a ratio that reflects the water component of carbohydrates. This close relationship with water is specifically why carbohydrates are often thought of in terms of their molecular composition.

This composition is consistent across various types of carbohydrates, whether simple sugars like glucose or more complex forms like starch. Their structure and function in biological systems, as energy sources and structural components, depend on this specific combination of elements. The other choices include elements that are either not components of carbohydrates or are found in different biological molecules, such as proteins or nucleic acids.