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 patient with IQ 30 will be diagnosed with: 
Select and explain. 
A. Mild mental retardation, B. Moderate mental retardation, C. Severe mental retardation, D. Profound mental retardation
C: Severe mental retardation
Answer: C: Severe mental retardation 
Explanation: Normal 90-109 Borderline 70-89 Mild MR 50-69 Moderate MR 35-49 Severe MR 20-34 Profound MR <20