You will be given a definition of a task first, then some input of the task.
In this task, you are given two facts, and a multiple-choice question. Based on the given facts, answer the question with index of the correct option (e.g, "A").

Fact1: Antigens are molecules that the immune system recognizes as foreign to the body., Fact2: Immunology is the study of the immune system., Question: What is one thing studied in immunology? (A) illness (B) antigens (C) humanism (D) health (E) philosophy (F) resistance (G) symbology (H) fever
Output:
B