Q: In this task, you are given a question and answer options for that question. Using this information, you have to classify each text into different topics: medicine, nursery, psychology, chemistry, pharmacology, biology.
Question: The oxygen we consume in the respiratory chain is transformed into: 
 Options:  <0> Acetyl-CoA. <1> Carbon dioxide. <2> Carbon monoxide. <3> Water. <4> Carbonic acid.
A:
biology