The Opportunity Cost of Producing One More Unit of a Good

The opportunity cost of producing one more unit of a good is calculated by dividing the

A) total quantity of that good by the total quantity of other good.
B) total quantity of the other good by the total quantity of the good whose opportunity cost we're calculating.
C) price of the good whose opportunity cost we are calculating by the number of units of the other good that are forgone.
D) increase in the quantity of that good by the decrease in the quantity of other good.
E) decrease in the quantity of the other good by the increase in the quantity of the good whose opportunity cost we're calculating.