Which of the following is a type of person who works for an organization only when they are needed?

A) on-call workers
B) moonlighting employees
C) apprentices
D) part-time employees
E) trainees

On-call workers are employees who work only when they are needed, typically in industries such as healthcare, hospitality, or customer service. They are not guaranteed a set number of hours and are called in as needed, often with short notice. Moonlighting employees may have a primary job and work part-time elsewhere for extra income, apprentices are individuals learning a trade or skill, part-time employees work a regular schedule but fewer hours than full-time employees, and trainees are individuals learning skills or knowledge for a specific job.