Selling skills contribute in a major way to four groups of knowledge workers who usually do not consider themselves salespeople:

Managerial personnel, Customer Service Representatives, Professionals, Entrepreneurs.

Explanation: Customer Service Representatives, Managerial personnel, Professionals and Entrepreneurs usually do not consider themselves to be Sales person or sales representatives. However, These four groups of people require expansive knowledge of the company's products as lots of consumers or customers who wish to deal directly with the company will prefer to contact the manager or customer service personnel in other to get more accurate and concise information about the company's products. These four groups must be able to convince and clear doubting current and impending customers on why their products and services are the best.

it limits peoples’ voting options. hope it : )