Which scientific study focuses on the function of cells, tissues, and organs in the body?

The correct choice is physiology, which is the branch of biology that deals with the functions and processes of living organisms, specifically focusing on how cells, tissues, and organs work and interact within the body. Physiology provides insights into the mechanisms that allow organisms to survive, grow, and respond to their environment. It encompasses various areas, including cellular processes, systemic functions, and the regulation of bodily systems.

For example, through the study of physiology, one can understand how the heart pumps blood, how the lungs facilitate breathing, and how muscles contract. This knowledge is vital for medical professionals, as it lays the groundwork for understanding health, disease, and the overall functioning of the body.

Other related fields such as pathophysiology focus on the changes in bodily functions due to disease, anatomy emphasizes the structure of the body rather than its function, and homeostasis pertains to the maintenance of stable internal conditions but does not directly focus on the functions of the body's systems. Hence, physiology is the most appropriate choice when referring specifically to the functions of cells, tissues, and organs.