I know this is a little late but i thought i should still tell you that its the endocrine organ
        
             
        
        
        
Answer:
The two organisms are in a predator-prey relationship.
Explanation
because the hawk is the predator, it ate the mouse, and th mouse was they prey, it was eaten 
 
        
                    
             
        
        
        
Answer: C.
because I translated it to what the answer is 
 
        
             
        
        
        
Answer:
Serotonin is an important chemical and neurotransmitter in the human body. it is believed to help regulate mood and social behavior, appetite and digestion, sleep, and memory