The Opportunity Cost of a Hot Dog in Terms of Hamburgers

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

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