(A) A description of a problem in one area of economics, followed by a revision of the description for two other areas.
(B) A description of a problem in one area economics, followed by a successful counter-example, then the description of a problem in a second area.
(C) A description of the successful application of economics to one subject, followed by a description of its limitations in two other areas.
(D) A description of one area of economics, whose problems are compared with those of two other areas of economics.
(E) A critical distinction between problems in two separate areas of economics.