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: Social & Preventive Medicine
Chronological age 10yrs, mental age 4yrs. What that person called as? 
Select and explain. 
A. Idiot, B. Imbecile, C. Normal, D. Genius
B: Imbecile
Answer: B: Imbecile 
Explanation: Ans. is 'b' i.e., Imbecile