Given the task definition and input, reply with output. 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 interaction between the urea cycle and the citric acid cycle is carried out at the level of: 
 Options:  <0> Uric acid. <1> Succinate <2> Ammonia. <3> Urea. <4> Fumarate

pharmacology