<prompt> IQ 20-34 -Severe MRProfound MRModerate MRMild MR  <response>: WHO classification of mental retardation MR mild MR ...IQ 50-70 moderate MR...IQ 35-49 severe MR...IQ 20-34 profound MR... IQ undere 20 ref; page no;582 23rd edition of PARK;s textbook of Preventive and Social medicine 