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: Urea:
Options: <0> It is transported to the liver for elimination. <1> It is degraded to ammonium in the urea cycle. <2> It is apolar and easily forms crystals. <3> It is obtained from arginine. <4> It has two ketone groups and one amino group.
biology