Among the options provided, Advertising Consultants are most likely to be self-employed.
Advertising consultants often work independently, offering their services to various clients and businesses on a freelance basis. They can manage their own schedules, choose their clients, and tailor their services to meet specific needs.
While Sales Representatives can also work independently, many are employed by companies. Human Resources Administrators and Training Specialists are typically employed by organizations and are less likely to be self-employed.