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: Unknown
Illusion is - 
Select and explain. 
A. Feeling of familiarity with unfamiliar thing, B. Altered perception of real object, C. Belief in something even though the same is proved false, D. Perception occurring without external stimulation
B: Altered perception of real object
Answer: B: Altered perception of real object 
Explanation: Ans is 'b' i.e. Alteration of perception of one's reality o Altered perception of real object - Illusiono False perception without external stimulus - Hallucination.Illusiono Illusions are altered perception in which a real external object is combined with imagery to produce false internal percept. In simple words, illusion is misinterpretation of an actual sensory input. For example:-i) Hearing once name in a train whistle:- Train whistle is a real external stimulus, which is perceived as once name (false internal percept).ii) Mistaking a stick or rope for snake in dark room:- Stick is a real external object, which is perceived falsely as snake.In illusion:-i) Sensory input is in external atmosphere.ii) Percept is in internal atmosphere (inner subjective space, i.e., inside the mind).o Illusions are most commonly seen in delirium.