For optimal performance, what is crucial regarding the placement of SPDs?

The correct answer emphasizes the importance of minimizing lead length for Surge Protective Devices (SPDs) because the length of the leads can significantly affect the performance of the device. When the lead length is kept short, it reduces the inductance that can occur in the circuit. High inductance can lead to increased voltage spikes and diminish the SPD's ability to protect electrical equipment from transient voltages.

Additionally, shorter lead lengths help in ensuring that the energy from a surge is more effectively diverted to ground, thereby protecting sensitive equipment. In practical applications, minimizing lead length optimizes the response time of the SPD during a surge event, allowing it to perform its protective function more efficiently.

The other choices do not align with this critical consideration. Placing SPDs out of view or connecting them to the nearest appliance does not necessarily increase their effectiveness. Furthermore, placing SPDs outside is not always suitable, as they need to be protected from environmental factors while ensuring optimal performance within an electrical system.