Which components are part of the 31-gpm circuit?

The components listed in the first choice are essential parts of a hydraulic system specifically designed for cranes. The main control valve regulates the flow of hydraulic fluid through the circuit, allowing the operator to control the crane's movement efficiently. Relief valves serve a critical safety function by protecting the hydraulic system from excessive pressure, which could lead to equipment failure or accidents. Joystick manipulators provide the operator with the interface needed to command various functions of the crane intuitively. Hydraulic swivels allow for fluid transfer between stationary and moving parts, ensuring continuous operation without causing damage or functional disruptions. Together, these components facilitate the operation of a hydraulic circuit rated at 31 gallons per minute, which is significant for maneuvering heavy loads and executing precise movements in crane operations.

In contrast, the other choices focus on parts that are not relevant to the hydraulic circuit. Fuel injectors and gears are associated with engine components, while the steering mechanism and outriggers relate to the crane's stability and movement but do not define the hydraulic system's operation. Winches, chains, and trailers are typically involved in lifting and towing aspects but fall outside the scope of a hydraulic circuit analysis. This differentiation solidifies the understanding that the hydraulic components are specific to crane operation and its efficiency in handling loads