C. Macrophages
When Macrophages approach a foreign pathogen they ingest the pathogens through phagocytosis, the Macrophages show the foreign antigen proteins on their cell surfaces.
The Helper T Cell recognizes the antigen on the surface of the macrophage and starts an immune response to the invading pathogen by sending out a chemical message
After that the B-cells produce antibodies that are specific to the antigens of the pathogens that slow them down so the macrophages can engulf them.