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").
Q: Fact1: burning wood is used to produce heat, Fact2: Combustion-related, motor vehicles, wood burning, open burning, industrial processes., Question: Combustion is used to produce what (A) energy (B) carbon (C) heat (D) earthquakes (E) air (F) oil (G) O2 (H) water
A:
C