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: Mammals generate heat mainly by keeping their metabolic rate high., Fact2: Aerobic exercise also contributes to the increased the metabolic rate., Question: Mammals can generate heat by (A) hibernation (B) layers of fat (C) perspiration (D) aerobic exercise (E) respiration (F) exercise (G) with their fur (H) to stay warm
Output:
D