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
Which of the following works on relaistic principle according to structural theory of mind 
Select and explain. 
A. Id, B. Ego, C. Preconscious, D. Super ego
B: Ego
Answer: B: Ego 
Explanation: Id works on pleasure principle
Superego works on morality principle
Ego works on reality principle & balances between Id & superego.