Final answer:
The ABC Company's incorrect statement about the Marston Company's product quality is an example of libel, which caused a decrease in Marston's sales.
Step-by-step explanation:
The incorrect statement published by the ABC Company about the quality of the Marston Company's product constitutes libel. Libel refers to a false statement made in writing that damages a person's reputation. In this case, Marston's sales dramatically decreased as a result of the false information published by ABC Company.