Answer:
The cytoplasm probably.
Explanation:
If there was cell membrane as an option, I would probably select cell membrane as the answer instead. The cell wall is fully permeable hence does not play a role in maintaining cell homeostasis, but rather plays a role in structural integrity of a plant cell. The mitochondria provides energy for cellular processes, not so much of maintaining cell homeostasis. The cytoplasm maintains a constant environment for cellular processes to take place hence would be the best answer out of all the three.
