Final answer:
Oxytocin is a hormone that not only stimulates uterine contractions during childbirth in a positive feedback loop but also enhances sexual behavior by promoting closeness and intimacy. The correct option is B.
Step-by-step explanation:
Oxytocin is an endocrine hormone secreted by the pituitary gland that plays a critical role in childbirth, lactation, and aspects of human behavior, particularly in the context of relationships and sexual activity.
During childbirth, oxytocin causes contractions of the uterine wall muscles, which strengthen as more oxytocin is released, exemplifying a positive feedback mechanism.
Beyond its well-known functions in childbirth and lactation, oxytocin is also involved in social bonding and has been found to be associated with behaviors that enhance closeness and sexual intimacy, thus the correct answer is b) Oxytocin enhances sexual behavior.