White blood cells, which are also called leukocytes, function by:

• A. producing the body's erythrocytes.
• B. producing blood-clotting factors.
• C. protecting the body from infection.
• D. carrying oxygen and other nutrients.

Answer: (C)

White blood cells, or leukocytes, play a crucial role in the immune system by protecting the body from infections and foreign invaders. They are essential for identifying and eliminating pathogens such as bacteria, viruses, and other microorganisms that can cause disease. The presence of various types of white blood cells, such as lymphocytes, neutrophils, and monocytes, allows the body to mount a specific immune response, which is vital for maintaining health and preventing illness.

This protective function is achieved through processes such as recognizing antigens, producing antibodies, and directly attacking infected or cancerous cells. The ability of white blood cells to adapt and respond to a wide range of threats is a key part of the body's defense mechanisms. In contrast, other options refer to different functions within the body that do not pertain to the role of white blood cells in immune defense, highlighting the distinct role leukocytes play in the overall function of the circulatory and immune systems.