Definition: 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: In its origins, the technique of Systematic Desensitization was explained from: 
 Options:  <0> Operant conditioning. <1> Conditioning in a single trial. <2> Classical conditioning. <3> Vicar conditioning. <4> Instrumental conditioning.
Output:
psychology