Which of the following is an example of a negative feedback loop?

during lactation, as an infant suckles, it stimulates the release of prolactin in the mother. prolactin causes more milk to be produced for the infant to suckle. this continues until the infant stops breast feeding.

baroreceptors in the arteries send a signal to the brain that the blood pressure is low. the brain sends a chemical signal to the heart to increase its rate of pumping. this continues until the baroreceptors sense a normal blood pressure.

during blood clotting, chemicals are secreted by wounded tissues that recruit platelets to the area. as the platelets arrive, they secrete more of the same chemicals, recruiting more platelets to the wound. this continues until the wound is clotted.

during childbirth, pressure on the cervix stimulates the release of oxytocin. this causes contractions, and therefore puts more pressure on the cervix. this cycle continues until the baby is born.