The failure to classify individuals having mental disorders may occur for a number of reasons, according to Halleck (1987). Which of these is NOT one of them?

a) Offenders may perceive mental illness as a weakness and want to avoid being diagnosed
b) Offenders may try to disguise their symptoms while in prison to avoid being medicated
c) Offenders may want to get whatever drugs they can while incarcerated
d) Offenders may not recognize that they are ill at all