Detailed 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'.
Problem:Question: What element plays a physiological role in the prevention of gastroesophageal reflux?
Options: <1> Upper esophageal sphincter <2> Angle of His. <3> Hernia of Hiato. <4> Purkinje angle. <5> Pyloric sphincter
Solution:
2