Which of the following is responsible for homeostasis on a cellular level?

Temperature regulation is an important bodily function for warm-blooded animals, because it allows them to live in any climate and to survive in places where the climate fluctuates seasonally. Homeostasis is important not only in regulating temperature but in performing tasks, such as digestion and elimination of waste. When an animal's kidneys filter its liquid intake and triggers the elimination of waste in the form of urine, that animal's body is performing a natural, involuntary function that helps regulate the amount of potentially toxic or otherwise harmful materials in the body. Homeostasis is important all the way down to the cellular level; without proper homeostasis, cells cannot perform essential tasks such as osmosis, which is a process of water passing through a cell's membrane.

Ithink the answer is a