Which of the following is not a correct use of the term opportunity cost?

a$)$ Opportunity costs are considered period costs rather than inventoriable costs for accounting purposes.

b$)$ Opportunity costs must be considered by managers when making decisions.

C$)$ Opportunity cost plus the incremental future revenues and costs equal the relevant revenues and costs of any alternative when capacity is constrained.

d$)$ The opportunity cost of holding inventory is the income forgone by tying up money in inventory and not investing it elsewhere.