7. Which of the following statements regarding costs and decision-making is correct? A. Fixed costs must be considered only on a per-unit basis. B. Per-unit fixed cost amounts are valid only for make-or-buy decisions. C. Per-unit fixed costs can be misleading because such amounts appear to behave as variable costs when, in actuality, the amounts are related to fixed expenditures. D. Sunk costs can be misleading in make-or-buy decisions because these amounts appear to be relevant differential costs.