What process do animals use to intake oxygen and expel carbon dioxide?

• A. Circulation
• B. Digestion
• C. Respiration
• D. Reproduction

Answer: (C)

Animals use respiration to intake oxygen and expel carbon dioxide. This biological process involves taking in oxygen from the environment, which is then transported to the cells through the bloodstream. Within the cells, oxygen plays a crucial role in cellular respiration, where it is utilized to produce energy by breaking down glucose.

As a byproduct of this energy production, carbon dioxide is generated. The carbon dioxide needs to be expelled from the body to maintain the proper function of cells and to avoid toxicity. This is achieved by transporting it back to the lungs, where it is exhaled.

In contrast, circulation refers to the movement of blood throughout the body, digestion involves the breakdown of food for nutrient absorption, and reproduction relates to the biological processes that result in the production of offspring. While all of these processes are essential for life, only respiration directly pertains to the exchange of gases, making it the correct answer in this context.