This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Psychiatry
Irresistible urge to do a thing repeatedly is seen in- 
Select and explain. 
A. Obsessive - compulsive disorder, B. Schizophrenia, C. Schizoaffective disorder, D. Depression
A: Obsessive - compulsive disorder
Answer: A: Obsessive - compulsive disorder 
Explanation: OCD is an anxiety disorder, which is characterized by recurrent, unwanted thoughts (obsessions) and repetitive behaviors (compulsion).