In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.

Question: Why do ovarian cycles not appear in nursing mothers for several months after birth ?:
Options: <1> For stress and lack of sleep associated with breastfeeding. <2> Because there are low levels of FSH and LH. <3> Because there are high levels of oxytocin. <4> By saving iron that is derived from breastfeeding. <5> Because there are high levels of progesterone.
2