I think the answer is evolution. 
 
        
             
        
        
        
Answer:
Parasympathetic nervous division
Explanation:
The parasympathetic division of nerves is a part of the autonomic nervous system which gets activated during the relax conditions.
The parasympathetic nervous system is the opposite of the sympathetic nervous system which gets activated during the stress condition.
The parasympathetic division gets activated when the level of cortisol and adrenaline gets decreased and the body responds by detoxifying, digesting and building immunity.
Thus, Parasympathetic nervous division is the correct answer.
 
        
             
        
        
        
Attached to the packaging of a food shipment 
        
             
        
        
        
In the United States, flu season occurs in the fall and winter. While influenza viruses circulate year-round, most of the time flu activity peaks between December and February, but activity can last as late as May.