Instructions: 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: The term that includes the changes of the endometrium during pregnancy is: 
 Options:  <1> Hatching. <2> Apposition. <3> Accession. <4> Invasion. <5> Decidualization.
Output:
5