The correct answer is D. Of wages foregone by the owner of the firm.
An implicit cost is a cost that a firm incurs but does not pay out in cash. It is the opportunity cost of using resources that could be used for other purposes. In this case, the owner of the firm could be working for someone else and earning a wage. By choosing to start their own business, they are forgoing this wage. This is an implicit cost of the firm.
The other options are all explicit costs. These are costs that the firm pays out in cash. Option A is the cost of worker wages and salaries. Option B is the cost of leasing a building. Option C is the cost of production supplies.
Implicit costs are important because they can affect the firm’s decision-making. For example, if the implicit cost of owning a business is high, the firm may be less likely to start or expand.