This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Microbiology
Defence Mechanism which explains "compulsions" in a patient with obsessive-compulsive disorder? 
Select and explain. 
A. Reaction formation, B. Regression, C. Undoing, D. Displacement
C: Undoing
Answer: C: Undoing 
Explanation: Three ego defence mechanisms of obsessive-compulsive disorder are isolation, undoing, and reaction formation.The role of defence mechanism isolation is to safeguards a person from anxiety-provoking impulses. Undoing is associated with a compulsive act that is carried out in an effo to stop or undo the consequences that the patient unreasonably foresees from a threatening obsession.Reaction formation involves evident patterns of behaviour and consciously experienced feelings and thoughts that are paicularly contrary to the underlying impulses.