Answer:
a. post-purchase cognitive dissonance.
Explanation:
Cognitive dissonance: It occurs as a consequence of an inconsistency between a consumer's decision and consumer's prior appraisal.
Post Purchase Cognitive Dissonance: This is the expression we give to the state of agitation which is there in the customer's mind after purchasing a product or service.
Example: After buying a car someone thinks they paid too much for it.