Detailed 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.
Q: Question: What two non-protein amino acids participate in the urea cycle ?:
Options: <0> Proline and hydroxyproline. <1> Ornithine and citrulline. <2> Alanine and arginine. <3> Oxalacetate and malate. <4> Serine and GABA.
A:
pharmacology