Which cells activate t-cells by antigen presentation?
b-cells b-cells
b. bacteria
c. macrophages
d. plasma cells

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.

The basic repeating unit of nucleic acids are known as nucleotides. a nucleotide consists of three distinct chemical groups.