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: volcanic ash in the atmosphere decreases the temperature by blocking the sun, Fact2: Small temperature variations can have major effects on natural ecosystems., Question: What can volcanic ash in the atmosphere do to natural ecosystems? (A) Create wealth (B) negative feedback (C) rapid changes occur (D) Major effects (E) erosion (F) No effect (G) Forest fire (H) Start engines
Output:
D