Answer:
The carbon-dioxide exists in the atmosphere, and it is dissolved in the water. 
Explanation:
With the process of photosynthesis, it becomes organic, and by breathing, the organic gas goes back to carbon-dioxide. 
The assimilation of carbon is the process when the carbon-dioxide converts to organic carbon with the help of living organisms. This organic carbon is then used for energy.
 
        
             
        
        
        
Photosynthesis is the process by which plants, some bacteria and some protistans use the energy from sunlight to produce glucose from carbon dioxide and water. This glucose can be converted into pyruvate which releases adenosine triphosphate (ATP) by cellular respiration. Oxygen is also formed.
Let me know if this helps! (。・ω・)ノ゙♥️
        
                    
             
        
        
        
A. The onset of the menstrual flow
        
                    
             
        
        
        
Answer:
Homologous structures provide evidence for common ancestry
 
        
             
        
        
        
True due to the hormones that act upon the kidneys Two examples being Antidiuretic Hormone (ADH) and Aldosterone 
ADH increases water permeability of the kidney tubules and Aldosterone decreases the Sodium in the urine and increases the Potassium.