Antigen processing and presentation is a way for viruses to infect cells. is the way foreign cells engulf macrophages. is a way for a cell to give information about its activities. is only accomplished by bacterial cells

is a way for a cell to give information about its activities.

Explanation:

Antigen processing refers to the process during which the antigens are degraded into small fragments. The small antigenic fragments that join the MHC molecules. The antigen-MHC complex is then presented on the surface of the plasma membrane of antigen-presenting cells. In this way, antigen processing and antigen presentation inform other immune cells about the presence of antigens/pathogen in the body.

For example, the T cells present in the lymphatic tissues are activated when they recognize the antigen-MHC II complexes and trigger the adaptive immune response.