Mystery Shoppers Are People

Mystery shoppers are people

A) hired by a firm to get legal,though not necessarily ethical,information about competitive firms.
B) hired by a firm's employees to prove to the courts that competitors are using unfair pricing practices.
C) hired by a customer to report on illegal or unethical practices that are regularly taking place at a particular establishment.
D) who pose as customers to check on availability and pricing of a firm's products or services and on the quality of the customer service provided by employees.
E) hired by law firms to check on the safety of their clients' products and the credibility of their advertising.