The correct answer is a. white blood cells. White blood cells, also known as leukocytes, are involved in the body's immune response and help fight infections. They can identify and attack foreign invaders such as bacteria and viruses, and they also play a role in inflammation and wound healing. Red blood cells, or erythrocytes, are responsible for carrying oxygen to the body's tissues. Fibrinogen is a protein involved in blood clotting. While all of these components are important for maintaining a healthy circulatory system, only white blood cells are directly involved in fighting infections.
~~~Harsha~~~