Below freezing point how animal get their body warm?

Animals that live in below freezing point temperatures get their bodies to become warm by:

-Eating food that would generate energy, or eat a lot of high energy food

-The way they behave (Behavioral adaptation)

-Be very well insulated (a lot of stored fat and externally with fur)

- Sea animals never leave the scene

The animals that live in below freezing temperatures are mostly warm-blooded.

answer; ///i believe that the correct answer is (a) specialized cells)

i thinking chemical change