This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Child psychiatry, Subject name: Psychiatry
A 16-year-old male is found to have a mental age of 9 years on I.Q. testing. He has 
Select and explain. 
A. Mild mental Retardation, B. Moderate mental retardation, C. Severe mental retardation, D. Profound mental retardation
A: Mild mental Retardation
Answer: A: Mild mental Retardation 
Explanation: IQ is (Mental age/ Chronological age) multiplied by 100. Here is it (9/16)* 100 which is 56. IQ is classified as Mild (50-69), Moderate (35-49), Severe (20-34) and Profound (<20). Ref: The ICD-10 Classification of behavioural and mental disorders, CDDG, pg 171.