during periods of strong economic activity, low unemployment, and wage growth, it is likely that some fast food restaurants may experience a decline in sales even if they have not altered their menu prices thereby resulting in shifting of the demand curve. which of the following best explains the shifting of the demand curve in this scenario? a. use of penetration pricing by fast food restaurants. b. increase in regulation of fast food prices. c. lower degree of price elasticity associated with fast food. d. all the listed options are reasons behind shifting of the demand curve. e. income effect prompting customer migration to non-fast food/full service restaurants