What must an operator remember before using the LHS hydraulic selector switch?

Answer: B — Engine must be at idle

The correct answer is that the engine must be at idle before using the LHS hydraulic selector switch. This is crucial for ensuring safe and effective operation of the hydraulic systems on the vehicle. When the engine is at idle, it reduces the risk of any unintended movements or sudden surges in hydraulic pressure that could occur if the engine were running at higher RPMs. This precaution helps prevent accidents and prevents damage to the hydraulic components by ensuring they operate within their intended parameters. By adhering to this guideline, operators can manipulate the hydraulic systems smoothly and effectively, ensuring that they are in complete control of the vehicle's functions. Other factors, such as placing the vehicle in neutral or securing the parking brake, may contribute to safe operating procedures in a broader sense, but the critical condition specifically related to the operation of the hydraulic selector switch is that the engine should be at idle to prevent complications during hydraulic engagements and disengagements.