Task: Question Answering
Input (English): 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.
Output (English): 2