Excluding lines, which components are necessary to constitute a simple hydraulic system?

In a simple hydraulic system, the essential components work together to transmit power through the hydraulic fluid. The pump is a crucial element as it converts mechanical energy into hydraulic energy by generating flow and pressure. The reservoir plays a vital role in storing the hydraulic fluid, providing a source for the pump and accommodating any fluid displacement during system operation.

The selector valve is important because it directs the flow of fluid to various parts of the system, allowing for control over the operation of different actuators. The actuator, which can be a cylinder or hydraulic motor, converts the hydraulic energy back into mechanical energy to perform work, such as moving a load or providing rotational motion.

While other options include different combinations of components, they either include unnecessary elements or omit critical ones. For example, including a filter in option A is useful for maintaining fluid cleanliness, but it is not essential for the system to function. Similarly, components like motor, gauge, and coupling in option D pertain more to hydraulic systems that also involve mechanical energy transfer rather than the core hydraulic functionality. Thus, the combination presented in the correct answer encapsulates all necessary functions for a simple hydraulic system to operate effectively.