If There Is a Fall in All Factor Prices Faced

If there is a fall in all factor prices faced by a firm,

A) there will be a downward shift in the long- run average cost curve but not in the short- run average cost curve.
B) there will be no change in the cost curves in the long run.
C) the firm will move to a lower point on both its long- run and short- run average cost curves.
D) the firm will move to a lower point on its long- run average cost curve only.
E) both the long- run and short- run average cost curves will shift downward.