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: Proton pump inhibitor drugs are useful in the treatment of:
Options: <1> Constipation. <2> Corneal ulcer. <3> Peptic ulcer. <4> Traveler's diarrhea. <5> Crohn's disease.
Solution:
3