Final answer:
Macrophages exhibit the highest phagocytic activity among the given cell types, as they specialize in phagocytosing and destroying harmful organisms and play a critical role in the immune system.
Step-by-step explanation:
Among the choices given, macrophages exhibit the highest phagocytic activity. Macrophages are specialized cells involved in the detection, phagocytosis, and destruction of bacteria and other harmful organisms. Furthermore, they can also present antigens to T cells and initiate inflammation by releasing cytokines that activate other cells. In contrast, basophils and eosinophils play roles in allergic reactions and parasite defense, erythrocytes (red blood cells) are primarily responsible for carrying oxygen, and B-cells are involved in the adaptive immune system, specifically producing antibodies.