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: Shivering occurs when many muscles contract a little bit all at once., Fact2: Heat production is increased by shivering and non-shivering thermogenesis ., Question: what happens when many muscles contract a little bit all at once? (A) heat is produced (B) To keep their body heat. (C) biceps (D) sweating (E) digestion (F) rapid expansion (G) preventing heat transfer (H) death
Output:
A