Which four elements make up over 95% of the human body?

The four elements that make up over 95% of the human body are oxygen, carbon, hydrogen, and nitrogen. These elements are fundamental to the structure and function of biological molecules.

Oxygen is a major component of water, which makes up a large portion of the human body, and it is also critical for cellular respiration—a process that produces energy. Carbon serves as the backbone for all organic molecules, including proteins, lipids, carbohydrates, and nucleic acids, making it essential for life. Hydrogen, found in water and organic molecules, is involved in energy production and chemical reactions within the body. Nitrogen is a vital component of amino acids, which are the building blocks of proteins, and nucleotides, which make up DNA and RNA.

In contrast, the other choices include elements that, while important, do not collectively contribute to over 95% of the body's composition. For example, iron, sulfur, phosphorus, sodium, potassium, calcium, and magnesium play crucial roles in various bodily functions, but they are present in much smaller quantities compared to oxygen, carbon, hydrogen, and nitrogen. Thus, the choice accurately reflects the primary elements essential for maintaining the structure and physiological processes of the human body.