The purchasing manager was able to bring down the cost of direct materials by purchasing direct materials of a slightly lower grade quality than the company had used previously. The lower grade of direct materials, however, meant a higher defect rate on the assembly line and a higher waste of direct materials during production, which in turn lowered operating income. This would have led to a(n) ________.

1 A. favorable direct labor cost variance

B. favorable direct labor efficiency variance

C. unfavorable direct materials efficiency variance

D. unfavorable direct materials cost variance