S part of her annual review of her company's budgets versus actuals, Mary Gerard isolates unfavorable variances with the hope of getting a better understanding of what caused them and how to avoid them next year. The variable overhead efficiency variance was the most unfavorable over the previous year, which Gerard will specifically be able to trace to: A. Standard direct labor hours below actual direct labor hours. B. The standard variable overhead rate below the actual variable overhead rate. C. Actual production units below budgeted production units. D. Actual overhead costs below applied overhead costs.