Definition: 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: Which compound acts as a sulfhydryl buffer and as an antioxidant? 
 Options:  <1> Glycogen <2> Glutamic acid. <3> Glucagon. <4> Glutathione <5> Ascorbic acid.
