What is the difference of the polynomials?

(–2x3y2 + 4x2y3 – 3xy4) – (6x4y – 5x2y3 – y5)

–6x4y – 2x3y2 + 9x2y3 – 3xy4 + y5
–6x4y – 2x3y2 – x2y3 – 3xy4 – y5
–6x4y + 3x3y2 + 4x2y3 – 3xy4 + y5
–6x4y – 7x3y2 + 4x2y3 – 3xy4 – y5

Kilgore trout creates a new scale to diagnose depression. however, his scale only assesses one symptom of depression while ignoring others. which of the following is his new scale most likely lacking? a) test-retest reliability b) discriminant validity c) criterion validity d) alternate-forms reliability e) content validity f) none of the above