The correct answer is: B. Marginal Cost
Marginal cost is the change in total cost that arises when the quantity produced changes by one unit. It is the additional cost incurred by producing one more unit of a good.
Abnormal cost is a cost that is not incurred in the normal course of business. It is a cost that is incurred due to some abnormal event, such as a natural disaster or a fire.
Fixed cost is a cost that does not change with the level of output. It is a cost that is incurred regardless of how much is produced.
Semi variable cost is a cost that is partly fixed and partly variable. It is a cost that changes with the level of output, but not in direct proportion to the change in output.
Sunk cost is a cost that has already been incurred and cannot be recovered. It is a cost that is irrelevant to future decisions.
Marginal cost is an important concept in economics and business. It is used to determine the optimal level of production and to make pricing decisions.