Answer: Option A
Explanation:
The exchange of the oxygen and carbon dioxide takes place in the lungs. The oxygen from the lungs are exchanged by the carbon dioxide between the alveoli and capillaries.
The oxygen from the lungs are carried away to various cells of the body and the carbon dioxide from the body cells are carried to the lungs for the process of exchange of gases.
Primary succession is beginning.
Secondary succession is beginning.
Primary succession is occurring