Q:Fact 1: Shivering occurs when many muscles contract a little bit all at once. Fact 2: Heat production is increased by shivering and non-shivering thermogenesis . Given the two facts above, answer the question "When many muscles contract a little bit, simultaenous, it produces:" with the following options: - forces - heat - cold blooded - sweat - electrical energy - Energy - pain - thermal displacement
A:
heat