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 of the following gases is the most abundant in the alveolar air? 
 Options:  <1> Oxygen. <2> Carbon dioxide <3> Water vapor. <4> Carbon monoxide. <5> Nitrogen.
