Instructions: 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.
Input: Question: Histidine and histamine are two compounds with biological importance that have in common as a structural unit: 
 Options:  <0> Pyridine <1> Piperidine <2> Triazine <3> Phenol. <4> Imidazole
Output:
chemistry