This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
The exact pa of the antigen that reacts with the immune system is called as - 
Select and explain. 
A. Clone, B. Epitope, C. Idiotope, D. Effector
B: Epitope
Answer: B: Epitope 
Explanation: An epitope, also known as antigenic determinant, is the pa of an antigen that is recognized by the immune system, specifically by antibodies, B cells, or T cells. Ref: Ananthanarayan & Panikers textbook of microbiology 9th edition pg:88