What is the primary role of white blood cells?

The primary role of white blood cells is to defend against infections. These cells, also known as leukocytes, play a crucial role in the immune system, identifying, attacking, and eliminating pathogens such as bacteria, viruses, and other foreign invaders that can cause diseases. There are several types of white blood cells, each with specific functions, such as phagocytes that engulf and digest pathogens, and lymphocytes that are involved in the adaptive immune response, targeting specific threats.

The other options describe functions related to other components of the blood. For example, the transport of oxygen throughout the body is performed by red blood cells, which contain hemoglobin that binds to oxygen in the lungs and carries it to tissues. Blood clotting is primarily facilitated by platelets, which aggregate at sites of injury to form clots and prevent excessive bleeding. Transporting nutrients is a function of plasma, the liquid component of blood, which carries nutrients absorbed from the digestive tract to cells throughout the body. Understanding the distinct roles of different blood components helps clarify why white blood cells are specifically responsible for immune defense.