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 can also generate little bursts of heat by shivering., Fact2: Heat production is increased by shivering and non-shivering thermogenesis ., Question: what do mammals use for heat? (A) thermogenesis (B) Animal fur (C) feet (D) Chemical energy (E) fur and fat (F) layers of fat (G) convection (H) ice
A