Final answer:
Hydrogen, nitrogen, carbon, and oxygen are major elements as they make up the majority of the human body and are necessary for forming essential biological molecules.
Step-by-step explanation:
The elements hydrogen, nitrogen, carbon, and oxygen, which account for 96% of the human body's make-up, are classified as major elements. These are found in large quantities in living organisms and are crucial for the formation of nucleic acids, proteins, carbohydrates, and lipids. Carbon, for instance, accounts for about 50 percent of the composition of the cell, making it fundamental to all macromolecules. The importance of these elements is demonstrated as they are necessary for a vast number of biochemical reactions and the construction of the structures that enable the functions of living organisms.