Product differentiation: group of answer choices a. is successful if a firm faces a relatively inelastic demand curve. b. cannot be accomplished through advertising or trivial product changes. c. is carried out by both perfectly competitive and monopolistically competitive firms. d. if carried out successfully enables the firms to enjoy market power. e. does not allow the firm to raise its price without losing all of its customers.

Asample of digestive juice was removed from the stomach of a pig. the juice was placed in a test tube along with some grains of wheat. a second test tube was set up containing an equal number of wheat grains, with distilled water rather than digestive juice. the test tubes were kept for 8 hours at 40 degrees c. after 8 hours, the grains inside the digestive juice had broken into tiny particles. the grains of wheat, in the water, were wet but otherwise unchanged. what is the control group?