Which part of a hydraulic jack contains the oil necessary for operation?

The cylinder is the correct part of a hydraulic jack that contains the oil necessary for operation. In hydraulic systems, oil acts as the medium for transferring force. When the plunger is pressed, it pushes the oil into the cylinder, creating pressure that lifts the load. The cylinder must be designed to hold this fluid and withstand the pressure generated during operation. It not only contains the oil but also facilitates the movement of the plunger, allowing for the lifting mechanism to work effectively. The other components, while essential to the overall function of the jack, do not serve the primary role of holding the hydraulic oil.