Which Provides the Best Description of Severe Mental Illness (SMI)

Which provides the best description of severe mental illness (SMI) ?

A) Having been clearly diagnosed with at least two mental health disorders within the past year
B) Having a diagnosable mental disorder with moderate functional behavior in a specific area of lifestyle at any time during the past year
C) Being unable to function in society because of a mental illness
D) Being convicted of several impulsive crimes during the past year