Answer:
D
Explanation:
The atmosphere is not an eycosystem
B oxygen because they need it to survive
Answer:
The human system is a complicated living organism that is structured of internal and external organs and fluids. It has the heart, liver, kidneys, stomach, large and small intestines, brain, and skin.
Intercalated disks are unique to cardiac muscles.
The development of offspring takes place inside the UTERUS