How do the muscles in thermoregulation?

a: muscles produce oil that burns in the presence of oxygen.
b: muscles undergo a chemical reaction that absorbs heat.
c: muscles break down carbon dioxide, producing heat.
d: muscles contract rapidly, producing heat.

Option D

Explanation:

Thermoregulation can be defined as the phenomenon of the body by which it regulates the temperature inside the body. The internal temperature of the body has to be maintained even if the temperature in the outer environment is changing.

In case the body encounters colder environment, the muscles of the body contract rapidly producing heat.

The contraction of the muscle requires  hydrolysis of ATP molecules which in turn releases energy in the form of heat. This heat is used by the body to maintain an optimum temperature within the body.

i think its the first one