Given the task definition and input, reply with output. 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: Immunity results from immunization., Fact2: Serious side effects resulting from vaccination are extremely rare., Question: What leads to immunity and extremely rarely with serious side effects? (A) hydration (B) peachleaf willow (C) homeopathy (D) veterinarians (E) vaccination (F) Allergies (G) exposure (H) Chemical energy
E