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: Lymphocytes are the key cells involved in the immune response., Fact2: An allergy attack is an immunal response., Question: Lymphocytes are the key cells involved in what (A) Veins and arteries. (B) permineralization (C) the skin (D) Animal survival (E) allergy attack (F) positive (G) massive damage (H) critical organs
Output:
E