The Opportunity Cost of a Hot Dog in Terms of Hamburgers

The opportunity cost of a hot dog in terms of hamburgers is the

A) ratio of the slope of the demand curve for hot dogs to the slope of the demand curve for hamburgers.
B) ratio of the slope of the supply curve for hot dogs to the slope of the supply curve for hamburgers.
C) money price of a hot dog minus the money price of a hamburger.
D) ratio of the money price of a hot dog to the money price of a hamburger.