You are presented with the quiz "what do mammals use for heat?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "mammals can also generate little bursts of heat by shivering" and "heat production is increased by shivering and non-shivering thermogenesis ". So, what's the best answer to the question?

Options:
a). thermogenesis.
b). Animal fur.
c). feet.
d). Chemical energy.
e). fur and fat.
f). layers of fat.
g). convection.
h). ice.
Answer:
a).