Overview:
Oxytocin is a hormone that plays a crucial role in various physiological processes in the human body, especially in females. It is primarily known for its involvement in childbirth and breastfeeding. The correct answer to the given question is option B, which states that oxytocin causes strong uterine contractions during parturition. Let's understand this in more detail.

Role of Oxytocin in Parturition:
During childbirth, oxytocin is released from the posterior pituitary gland in response to the stretching of the cervix and vagina. This hormone acts on the smooth muscle cells of the uterus, causing them to contract. These contractions play a pivotal role in the progression of labor and the delivery of the baby. Oxytocin stimulates the rhythmic contractions of the uterus, which helps in the dilation of the cervix and the expulsion of the fetus through the birth canal.

Initiation of Labor:
Towards the end of pregnancy, the levels of estrogen in the body increase, leading to an increased sensitivity of the uterus to oxytocin. This increased sensitivity, along with mechanical stretching of the cervix and release of prostaglandins, triggers the release of oxytocin from the posterior pituitary gland. The release of oxytocin initiates labor by stimulating uterine contractions.

Strengthens Uterine Contractions:
Oxytocin acts on specific receptors present on the smooth muscle cells of the uterus. Binding of oxytocin to these receptors leads to an increase in the intracellular calcium levels, which ultimately results in the contraction of the uterine muscles. These contractions become progressively stronger as labor progresses, helping to push the baby out of the womb.

Positive Feedback Loop:
During labor, as the baby moves down the birth canal, the stretching of the cervix and vagina stimulates the release of oxytocin. The released oxytocin further enhances the uterine contractions, which, in turn, leads to more stretching and more oxytocin release. This positive feedback loop continues until the baby is delivered.

Conclusion:
In summary, oxytocin plays a crucial role in childbirth by causing strong uterine contractions. It is released in response to the stretching of the cervix and vagina, and its actions on the uterus help in the progression of labor and the delivery of the baby. The other options provided in the question, such as stimulating the secretion of vasopressin, being secreted by the anterior pituitary, or stimulating the growth of mammary glands, are not accurate with respect to the role of oxytocin in adult females.