What components are essential for the swing operation of the crane?

The essential components for the swing operation of a crane include hydraulic fluid and two swing cutout valves. Hydraulic fluid is critical because it transmits power throughout the hydraulic system, allowing for smooth and precise movement of the crane's swing function. Without the hydraulic fluid, the hydraulic cylinders that control the swing movement would not function properly, making it impossible to rotate the crane effectively.

The swing cutout valves play a vital safety role. They ensure that the hydraulic system can be controlled and shut off under certain conditions, preventing accidental movement or unintended swing operation. This is particularly important for maintaining the safety of the operator, equipment, and surroundings during crane operations.

These components work together to facilitate the crane's ability to pivot or swing, essential for positioning loads accurately. The other choices provided include components that may be important for different crane functions, but they do not directly relate to the swing operation.