A. A favorable material price variance means that the price of materials consumed by production was lower than budgeted. An unfavorable material usage variance means that the quantity of materials used by production was greater than the standard quantity. Both variances could be caused by the purchase and use of lower than standard quality material.

B. A favorable material price variance means that the price of materials consumed by production was lower than budgeted. However, an unfavorable material usage variance means that the quantity of materials used in production was greater than the standard quantity.

C. An unfavorable material usage variance could be caused by labor efficiency problems. However, a favorable material price variance does not relate to such problems.

D. An unfavorable material usage variance could be caused by labor mix problems. However, a favorable material price variance does not relate to such problems.