What is the function of the thymus gland?

The thymus gland plays a crucial role in the development and function of the immune system, specifically in the maturation of T lymphocytes, also known as T cells. These cells are essential for the adaptive immune response, which is the body's tailored defense against pathogens, including viruses and bacteria.

During childhood and adolescence, the thymus is active in producing and maturing T cells, which help the body recognize and respond to foreign invaders. As a person ages, the thymus gradually shrinks and becomes less active, leading to a decrease in T cell production. This highlights the importance of the thymus in establishing a strong immune system during early life.

While the other choices involve important bodily processes—like metabolism, hormone production, and stress response—these functions are not the primary role of the thymus gland. Its specific and vital contribution to the immune system is what makes this answer correct.