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: Shivering occurs when many muscles contract a little bit all at once., Fact2: Another response to cold is shivering., Question: Many muscle fibers contracting at once can be induced by (A) exposed genitalia (B) exposure to heat (C) sweating (D) exposed biceps (E) mechanical waves (F) Electrical energy (G) exposure to cold (H) Veins and arteries.
G