Which signal-return wire design must be used to prevent electromagnetic interference?

The correct choice for preventing electromagnetic interference is shielded wires. Shielded cables are designed with a conductive layer that encases the wire's insulation. This layer can be made of various materials, including metal foil or braided wire, which serves as a barrier against external electromagnetic fields. By grounding this conductive shield, it helps to redirect interference away from the signal-carrying conductors, ensuring that the integrity of the signals being transmitted is maintained.

Twisted pairs, while effective in reducing interference due to the twisting action which helps cancel out electromagnetic interference, are primarily designed for differential signaling rather than outright shielding. Individual wires do not offer any protection against electromagnetic interference, making them less viable in environments where interference is a concern. Bundled wires, while they may keep multiple conductors organized, can still be susceptible to interference without additional shielding measures. Thus, the use of shielded wires is crucial in environments with potential electrical noise or interference to maintain high-quality signal transmission.