Final answer:
Mars Inc., with its wide range of advertising services, exemplifies a full-service agency that offers comprehensive marketing and advertising solutions.
Step-by-step explanation:
In the scenario described, Mars Inc., an advertising agency that offers a range of services such as sales promotion, marketing research, package design, direct marketing, publicity, and the planning, creation, and production of advertising, is an example of a full-service agency. This type of agency provides comprehensive solutions to clients' advertising and marketing needs, as opposed to specialized services that are characteristic of creative boutiques, media buying organizations, account service organizations, or media specialist companies.