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: insulated material can be used for keeping warm, Fact2: Insulators are materials that prevent the flow of heat., Question: Materials that prevent the flow of heat can be used for keeping what? (A) airy (B) power (C) warm (D) liquid (E) dry (F) energy (G) empty (H) down
Output:
C