Which of the Following Best Illustrates a Job Opening Being

Which of the following best illustrates a job opening being filled in a hidden job market?

A) Naomi found a job as an assistant fashion designer through a friend who works as a fashion photographer for a company.
B) Nathan found a job in a multinational company after he applied for it on the company's Web site.
C) Carla found a sales job in a departmental store through an advertisement in the local newspaper.
D) Walter found a job as a marketing executive in an automobile company through a private employment agency.