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: Substances that prevent abrupt changes in the pH of a solution by adding an acid or a base to it are called: 
 Options:  <1> Aceto-acetic bodies. <2> Tampons. <3> Hydrogens. <4> Anhydrous. <5> Answers 2 and 3 are the correct ones.
Solution:
2