Answer:
b. Alternative cost.
Step-by-step explanation:
Sunk cost is cost that has been incurred and cannot be recovered.
Out of pocket cost is a cost incurred out of an employees personal cash reserves for which he may be reimbursed for by his employers.
Differential cost is the cost of two different options.
Opportunity cost is the benefit lost when one alternative is chosen over other alternatives.
I hope my answer helps you.