Definition: 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'.
Input: Question: Prolactin stimulates the: 
 Options:  <1> Milk secretion <2> Milky ejection. <3> Deposit of fat in the breasts. <4> Formation of the mammary ducts. <5> Formation of mammary secretory cells.
