If you mean a specific system then the reproductive system...but i haven't the slightest idea as to anything else to do with your question...
Answer:
solid
Explanation:
Matter in solid state have the highest density, with the molecules tightly packed together.
Answer:
A. Respiration
Explanation:
The process in which oxygen atoms are made available to the cell of animals is called cell respiration. In cell respiration the food molecules undergo process which is called food oxidization, that make it available to be absorbed by the animal cell.
Sunscreen, sunglasses, hat, umbrella, under a tree where there’s shade