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: Given the suspicion of hypertrophic pyloric stenosis, how would you start the complementary exams?
Options: <1> Digestive transit. <2> Gastric pHmetry <3> Simple radiology <4> Ultrasound <5> Isotopic study
Output:
4