Which of the following is not a trace element in living organisms?

Carbon is considered a fundamental building block of life and is classified as a major element rather than a trace element. Trace elements are typically required by organisms in very small amounts, essential for various biological functions but not abundant in the body. Examples of trace elements include copper, iron, and zinc, all of which play crucial roles in enzymatic reactions, oxygen transport, and other physiological processes.

In contrast, carbon is a primary component of macromolecules such as carbohydrates, proteins, lipids, and nucleic acids, making it essential for the structural framework of living organisms. Thus, it is classified as a major element because it is found in much larger concentrations compared to trace elements.