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
A 8 year old child after tonsillectomy sees a bear in her room. She screams in fright. A nurse who rushes in switches on the light, finds a rug wrapped on a armchair. She pacifies the child what the child experienced was a : 
Select and explain. 
A. Delusion, B. Illusion, C. Hallucination, D. None of the above
B: Illusion
Answer: B: Illusion 
Explanation: A real object, i.e. rug wrapped on a armchair is misinterpreted as bear.