What is the main function of white blood cells?

The main function of white blood cells is to protect the body against infections and foreign substances. These cells, also known as leukocytes, are a crucial component of the immune system. They play an essential role in identifying and combating pathogens such as bacteria, viruses, and fungi, as well as responding to foreign materials and diseases.

White blood cells can be classified into different types, each with specific roles in immune response. For example, lymphocytes are responsible for targeting specific pathogens, while phagocytes engulf and digest cellular debris and microbes. Their ability to recognize and remember previous invaders also enables the body to mount a quicker and more effective response upon subsequent exposures to the same pathogens.

In contrast, the other functions listed in the choices relate to different types of blood cells or physiological processes unrelated to the immune function of white blood cells. Transporting oxygen is primarily the role of red blood cells, coagulating blood is a function associated with platelets, and hormone production is typically the responsibility of specific glands and cells, not white blood cells.