This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
[{'content': 'The term epitope refers to \nSelect and explain. \nA. Complete antigen molecule, B. Hapten, C. Immunogen, D. Smallest antigenic determinant', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]