Which of the Following Statements Is True

Which of the following statements is true?

A) Costs are always explicit, never implicit.
B) Costs are always implicit, never explicit.
C) George runs a stationery shop; he paid Frank $5,000 for the carpet he installed in the shop. The $5,000 for carpet is an implicit cost.
D) An implicit cost is a cost that represents the value of resources used in production for which no actual monetary payment is made.