Answer: Option C.
Step-by-step explanation:
Antigen is defined as a protein or polysaccharide that arises an immune response in lymphocytes. Antigen is a substance that binds to a specific antibody.
For human body, an antigen can be any substance that evokes immune response, Example: dust particle,pollen grain, any food particle. The interaction between antibody and antigen is defined from lock-and-key binding model.
Antigen receptor, are located on B cells and T cells, that binds to antigens and initiates potential immune responses.
Hence, the correct answer is Option C.