Concept:Carbon is the fundamental element that forms the backbone of all organic molecules in living things.
Explanation:Carbon is unique because it can form stable bonds with many elements, including hydrogen, oxygen, nitrogen, and itself.
This allows carbon to create large, complex, and diverse molecules.
These molecules include proteins, carbohydrates, lipids, nucleic acids, and other cellular components.
Together, they make up the structures and perform the functions needed for life.
Therefore, carbon is regarded as the major building block of an organism.
Answer:C. Carbon