Final answer:
Mike Walker, who supervises operations and is responsible for quality control, training, and scheduling on the assembly line, is best categorized as a C. First-Line Manager.
Step-by-step explanation:
Mike Walker supervises operations on the chassis assembly line for a large vehicle manufacturer. His responsibilities include spending most of his time in quality control, maintenance, scheduling workers, and training new employees. Based on the description of his duties, Mike Walker would be categorized as a C. First-Line Manager. First-Line Managers are directly involved in managing the work of non-managerial employees and typically handle day-to-day supervisory duties and the oversight of operational activities, which align with Walker's responsibilities.
Middle managers are responsible for supervising lower-level managers and employees and are typically involved in tasks such as quality control, employee scheduling, and training. Mike Walker, who supervises operations on the chassis assembly line and is involved in quality control maintenance, scheduling workers, and training new employees, would be categorized as a middle manager.