Answer:
The Sun
Explanation:
Nearly everything eats sunshine – or eats something else that ate sunshine. The Sun is the major source of energy for organisms and the ecosystems of which they are a part. Producers, such as plants and algae, use energy from sunlight to make food energy by combining carbon dioxide and water to form organic matter.
 
        
                    
             
        
        
        
HCL is guilty for triggering the release of enzymes such as pepsin which are essential for the digestion of protein. Bile contains bile acids, which are critical for digestion and absorption of fats and fat-soluble vitamins in the small intestine.
        
             
        
        
        
Answer:
b
Explanation:
the element is named after the latin word for calcium 'calx'
 
        
             
        
        
        
Answer;
I think it's d,possible spread of tropical diseases.
 
        
             
        
        
        
Answer:
Population.
Explanation:
Population may be defined as the smallest unit of ecology and the evolution might occur at the population level. 
Population is the group of the organisms that belong to the particular species and lives in a specific particular habitat. The individual of the population breeds among themselves. Sometimes the individual of two different population can also breed among themselves in extreme cases.
Thus, the answer is population.