You will be given a definition of a task first, then some input of the task.
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: Carbon monoxide is a gas produced by furnaces and other devices that burn fuel., Fact2: Gas furnaces heat homes for up to 20 years., Question: what produces carbon monoxide? (A) h2o (B) burning coal (C) hydrogen (D) freezing (E) heating homes (F) chlorofluorocarbons (G) cigarettes (H) gasoline
Output:
E