Which element is essential for respiration and is part of the air we breathe?

Oxygen is the element essential for respiration and is a critical component of the air we breathe. In the process of respiration, living organisms, including humans, inhale oxygen, which is necessary for the production of energy in the form of adenosine triphosphate (ATP). This energy production occurs in the mitochondria of cells through aerobic respiration, where oxygen helps metabolize glucose and other nutrients.

While carbon dioxide is a byproduct of respiration and nitrogen makes up a significant portion of the atmosphere, they do not serve the primary role that oxygen has in supporting the metabolic processes required for life. Hydrogen, while a component of water and organic molecules, is not directly involved in the respiration process in the same manner as oxygen. Therefore, oxygen's vital role in energy production through respiration underscores its importance as the correct answer to the question.