Final answer:
The two major elements that compose body mass are oxygen (O) and carbon (C), which are part of the four elements that make up over 95 percent of the body's mass.
Step-by-step explanation:
The two major elements that compose body mass are oxygen (O) and carbon (C). These two elements, along with hydrogen (H) and nitrogen (N), make up more than 95 percent of the body's mass. All matter, including the human body, is composed of a limited number of fundamental substances called elements, which are the building blocks of matter.
Each element's name can be replaced by a one- or two-letter symbol. Oxygen (O) is the most abundant element in the human body, followed by carbon (C). Together, all the elements in the body are derived from the foods we eat and the air we breathe. It's important to understand that while our bodies can construct many chemical compounds needed for life from elements, it cannot create the elements themselves—they must be absorbed from our environment.