When Considering Insanity as a Defense, What Is the Primary

When considering insanity as a defense, what is the primary question?

A) Does the accused understand the act to be criminal?
B) Does the offender suffer from some mental disease or defect that directly correlates to this inability to appreciate the fundamental illegality engaged in?
C) Has the offender previously been institutionalized for mental illness
D) All of the above
E) A & B only