This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cognitive development and defence mechanism, Subject name: Psychiatry
Pa of mind which is working on reality principle is 
Select and explain. 
A. Ego, B. Id, C. Ego-ideal, D. Super ego
A: Ego
Answer: A: Ego 
Explanation: Sigmund Freud gave Structural theory of mind. it is the cornerstone of ego psychology. Three provinces are- Id- reservoir of unorganised instinctual drives. It is more concerned with basic instincts. Ego- it is the executive organ of the psyche, controls motility, perception, contact with reality and through defense mechanisms available to it, the delay and modulation of drive expression. Superego- establishes and maintains an individual's moral conscience on the basis of a complex system of ideals and values internalised from parents. Ref: synopsis of Psychiatry, 11e, pg 159.