Given the task definition and input, reply with output. 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: burning wood is used to produce heat, Fact2: Heat is added and the temperature of the water increases., Question: What is used to increase temperature? (A) activation energy (B) ice (C) electricity (D) snow (E) glaciers (F) burning wood (G) Electrical energy (H) Fuel cells
F