Answer:
The answer is B. Sunk cost
Explanation:
Sunk cost are irrelevant again in business decisions.
A sunk cost has already been incurred. For example, a business that bought a machine which is no longer needed again. When making decisions, it is good to disregard the cost of machine. One cannot change a sunk cost.
Today's decision shud be based on present future cash flows when making investment decisions.