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: Any antigen that causes an allergy is called an allergen., Fact2: Antibodies are produced to fight antigens., Question: What are produced to fight allergens? (A) oxidizers (B) bacteria (C) flagella (D) antibodies (E) red blood cells (F) enzymes (G) hormones (H) orange
Output:
D