Final answer:
Carbon is the element that makes up all of the most common substances in your body, after hydrogen and oxygen.
Step-by-step explanation:
The element that makes up all of the most common substances in your body, after hydrogen and oxygen, is carbon. Carbon is found in a wide range of biomolecules, including carbohydrates, lipids, proteins, and nucleic acids. It plays a crucial role in the structure and function of living organisms.