When an economist uses the term "cost" referring to a firm, the economist refers to the

A) price of the good to the consumer.
B) explicit cost of producing a good or service but not the implicit cost of producing a good or service.
C) implicit cost of producing a good or service but not the explicit cost of producing a good or service.
D) opportunity cost of producing a good or service, which includes both implicit and explicit cost.
E) cost that can be actually verified and measured.

D