Twenty-Nine-Year-Old Brenda Has an IQ of 67, Yet She Finished

Twenty-nine-year-old Brenda has an IQ of 67, yet she finished fourth grade. She lives with her boyfriend, pays her bills with money she earns as a factor worker, and is able to live without supervision. What is Brenda's most likely diagnosis in terms of the DSM-IV classification of mental retardation (MR) ?

A) would be considered MR because of low IQ
B) would not be considered MR, because she is over 18
C) would be considered MR because of low educational status
D) would not be considered MR, because she is functioning adaptively