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 main stimulus for secretion of secretin is the presence in the duodenum of:
Options: <1> acid pH <2> Carbohydrates <3> Proteins <4> Hypoosmolar chimo. <5> Hyosmolar chyme.
Output:
1