What is the role of antibodies produced by B lymphocytes?

Antibodies produced by B lymphocytes play a crucial role in the immune system, particularly in identifying and neutralizing pathogens such as bacteria and viruses. When B lymphocytes encounter a specific antigen, they differentiate into plasma cells that produce antibodies. These antibodies bind to antigens on the surface of invading microbes, marking them for destruction or directly neutralizing their harmful effects. This action is essential for the body's defense against bacterial infections, as it helps prevent further spread of the bacteria and promotes their elimination by other immune cells.

The other roles mentioned, such as transporting oxygen, facilitating cellular respiration, and regulating blood clotting, are functions of different biological molecules and processes in the body. Hemoglobin, for example, is responsible for oxygen transport in red blood cells. Enzymes and cellular components are involved in cellular respiration, while various proteins, including clotting factors, play a role in blood clotting mechanisms. Therefore, the specific role of antibodies produced by B lymphocytes is to combat infectious agents, making option C the correct choice.