Answer:
D. the dynamic regulation of an organism's internal environment to maintain conditions suitable for survival.
Explanation:
Respiratory system= breathing system
To keep our Respiratory system healthy we should:
1- never breathe in front of polluted areas
2- never pollute our areas
3- try to make our environment normal
The answer is Vacuoles. After water enters this cell through the osmosis, it expands to absorb water and contract to release it.
