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: heat and pressure change the remains of prehistoric living things into natural gas, Fact2: Fossils are the remains of prehistoric life., Question: What two things turn fossils to natural gas? (A) heat and cold (B) heat and fuel (C) hydrogen and oxygen (D) heat and pressure (E) pressure and time (F) scarce resources (G) kinetic energy (H) chemical changes
Output:
D