What is the function of the tonsils in the body?

The tonsils play a key role in the immune system as part of the body's first line of defense against pathogens. Located at the back of the throat, the primary function of the tonsils is to filter foreign substances, such as bacteria and viruses, that enter the body through the mouth and nose. They contain immune cells that help detect and respond to these invaders, thereby playing an essential role in protecting the body from infections. This function is particularly critical in childhood, as the tonsils help develop the immune system during the early years of life.

The other options do not accurately represent the function of the tonsils. Producing red blood cells is primarily the role of the bone marrow. Regulating temperature is a function managed by the hypothalamus and other systems in the body, not the tonsils. Storing fat is related to adipose tissue, which serves a different purpose entirely. Thus, the tonsils' specific role in filtering foreign substances is what makes this answer correct.