On a Production Possibilities Frontier, the Opportunity Cost of One

On a production possibilities frontier, the opportunity cost of one more unit of a commodity per time period is measured by the

A) monetary price of the commodity
B) amount of the other commodity that must be sacrificed
C) amount of unemployed resources that must be used
D) amount of satisfaction it gives consumers
E) amount of tax paid to government for production, sale, and use of the commodity