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: increasing heat causes thermal expansion, Fact2: Fire puts off heat., Question: What causes thermal expansion? (A) fear (B) cold (C) coal (D) energy (E) Sun (F) fire (G) ice (H) wind
F