Final answer:
The "love" hormone discussed in this unit is oxytocin, which is associated with social bonding, childbirth, maternal behaviors, and lactation.
Step-by-step explanation:
The hormone commonly referred to as the "love" hormone is oxytocin. It plays a significant role in social bonding, sexual reproduction, childbirth, and the period after childbirth. Oxytocin is released in large amounts during labor, facilitating birth, promoting maternal bonding, and, postpartum, stimulating lactation. It is also associated with empathy, trust, and relationship-building, which is why it is often called the "love" hormone. So, in response to the original question, the correct answer would be option 4) oxytocin.