Below Are Some Financial Data for the Do Drop in Convenience

Below are some financial data for the Do Drop In convenience store.
The owners have put $40,000 into the business and they worked a total of 80 hours during the week.Savings accounts are currently paying 5.2% interest and the going wage rate is $8 per hour.
-What are sunk costs?

A) Costs that are implicit and are not actually paid out in money.
B) The historical costs of buying machinery and equipment which have no current resale value.
C) The annual cost of wear and tear on machinery and equipment.
D) Costs that are actually paid out in money.