Answer:
D.)
Explanation:
(I know this, by experience :|)
 
        
             
        
        
        
The hormone to be given is oxytocin. Oxytocin is a hormone produced by the paraventricular nuclei of the hypothalamus then stored in the posterior pituitary gland (along with antidiuretic hormone or vasopressin) that is responsible mainly for uterine contraction and milk ejection or letdown. Oxytocin induces contraction of the myoepithelial cells in the breast for milk letdown. On the other hand, there is upregulation of oxytocin receptors during parturition which makes the uterus more sensitive to oxytocin. Oxytocin is also known to induce labor and reduce post-partum bleeding.
 
        
             
        
        
        
According to my research it’s C: Nucleus
        
                    
             
        
        
        
the term was coined by the Charles Darwin in which he specifies two reasons for an organism to survive and reproduce 
1. Fitness. it is the ability of an organism to reproduce and survive in an environment
2. Adaptation. the inherited qualities and characteristics which increases chances of human survival.
the term is fitness