This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Mental Health, Subject name: Social & Preventive Medicine
Person at night looks at the window and frightens. Wife switches the light on and turns out that window cover is having a shape like a man. This is - 
Select and explain. 
A. Hallucination, B. Illusion, C. Delusion, D. Hyperacusis
B: Illusion
Answer: B: Illusion 
Explanation: Ans. is 'b' i.e. illusion o Altered perception of real object (i.e presence of external stimulus) - Illusiono False perception without external stimulus - Hallucination.# Here in this question external stimulus is present in the form of man shaped window cover. So it is an example of illusion.o A delusion is a disorder of thought content characterized by false, firm (unshakeable) belief that is not accepted by other members of patient's culture and societyo Hyperacusis is perceiving normal sounds as abnormally loud.