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
Smallest unit of antigenicity 
Select and explain. 
A. Epitope, B. Paratope, C. Idiotype, D. Hapten
A: Epitope
Answer: A: Epitope 
Explanation: Epitope of antigenic determinant is the smallest unit of antigenicity.