What is the main role of antibodies in immunity?

Antibodies play a crucial role in the immune system by specifically binding to antigens, which are foreign substances that can trigger an immune response, such as pathogens like bacteria and viruses. When antibodies bind to these antigens, they can neutralize them directly, inhibit their ability to infect host cells, or mark them for destruction by other immune cells. This process of binding and neutralization is essential for effectively eliminating pathogens from the body and preventing infections.

The correct answer highlights the primary function of antibodies in targeting and inactivating antigens, which is key to the adaptive immune response. Through their specificity and ability to interact with a variety of antigens, antibodies contribute significantly to the protection against diseases.

Other options refer to different aspects of immune function or biological processes. Memory of pathogens is primarily associated with memory B cells and T cells, which are involved in long-term immunity. Signaling other immune cells is a function performed by cytokines rather than antibodies. Transporting oxygen in blood is the role of hemoglobin in red blood cells, not antibodies. Therefore, the correct option correctly focuses on the vital role of antibodies in the immune response against pathogens.