Which of the following best describes the function of white blood cells?

White blood cells, also known as leukocytes, are a critical component of the immune system. Their primary function is to protect the body against infections and diseases. They achieve this through various mechanisms, including identifying and attacking pathogens, such as bacteria, viruses, and other foreign substances. White blood cells can also produce antibodies that further aid in the immune response.

This protective role is essential for maintaining health, as it helps the body respond to and eliminate threats that can cause illness. Their increased production in response to infection is a key indicator of an active immune response, highlighting their significance in defending the body against disease.

The other options describe functions associated with different components of the blood. For instance, transporting oxygen is primarily the role of red blood cells, while blood clotting is facilitated by platelets and clotting factors. Regulating blood pressure involves various mechanisms including the action of blood vessels and hormones, rather than white blood cells. Understanding the specific roles of each blood component helps clarify their unique contributions to overall health.