Final answer:
The four elements comprising over 96% of most living organisms' mass are carbon, hydrogen, nitrogen, and oxygen, which are essential to the structure and function of all biological molecules.
Step-by-step explanation:
The four elements that make up more than 96% of the mass of most living organisms are carbon (C), hydrogen (H), nitrogen (N), and oxygen (O). These elements are fundamental to the structure and function of living matter because they are the main building blocks for nucleic acids, proteins, carbohydrates, and lipids. Each of these elements plays a critical role in the biochemical reactions that facilitate life, with carbon forming four chemical bonds, nitrogen forming three, oxygen forming two, and hydrogen forming one. This chemical bonding capability allows for the formation of a vast number of diverse molecular species that make up the cells, tissues, and organ systems of organisms.