What action must a driver take upon encountering a red "X" sign on the airfield?

Answer: B — Cease all operations and refrain from entering the area

When a driver encounters a red "X" sign on the airfield, the appropriate response is to cease all operations and refrain from entering the area. The red "X" indicates that the area beyond the sign is closed or unsafe for entry, which is crucial for maintaining safety and operational integrity on the airfield. This sign serves a critical purpose; it alerts drivers to an immediate hazard or operational restriction, protecting personnel and aircraft from potential dangers. Following this directive is essential to prevent accidents and ensure compliance with airfield regulations. Understanding the significance of signage is key in airfield driving, as it directly relates to the safety of all operations within that environment. Therefore, when confronted with a red "X," the best course of action is to stop and avoid entering that restricted area.