Final answer:
Oxygen, carbon, hydrogen, and nitrogen are the four elements that make up about 96% of the mass of the human body.
Step-by-step explanation:
The four elements that combine to make about 96% of the mass of the human body are oxygen, carbon, hydrogen, and nitrogen. These elements are found in various molecules and compounds in the body and are essential for life processes. Oxygen is necessary for cellular respiration, carbon is the backbone of organic molecules, hydrogen is involved in many biological reactions, and nitrogen is a component of proteins and nucleic acids.