Definition: 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").
Input: Fact1: the emission of sulfur dioxide causes acid rain, Fact2: Acid rain effects forest ecosystems., Question: What causes damage to forest ecosystems? (A) flooding (B) humans disturb it (C) Sulfur dioxide (D) deforestation (E) Liquid bromine (F) Carnivore animals (G) Pollution (H) Hydrogen peroxide
Output:
C