Psychiatry General 15bed36b Mild mental retardation is characterized by A IQ : 90 - 109 B IQ : 70 - 89 C IQ : 50 - 69 D IQ : 35 - 49 High-Yield Explanation Normal : 90 - 109. Borerline : 70 - 89. Mild : 50 - 69. Moderate : 35 - 49. Severe : 20 - 34.