Portable electronic devices that may interfere with navigation systems may not be operated:

The correct answer emphasizes the importance of maintaining safety and operational integrity within controlled airspace. Operating portable electronic devices under Instrument Flight Rules (IFR) can potentially cause electromagnetic interference, which may compromise navigation systems critical for safe flight. IFR conditions require precise navigation and communication, as pilots may need to rely solely on instruments due to insufficient visibility or adverse weather conditions.

Under IFR, the potential for interference from personal electronic devices poses a significant risk. That is why regulations strictly prohibit their use in these scenarios to ensure that navigational aids function correctly and pilots avoid distractions that could lead to errors in instrument reading or communication.

The other choices suggest scenarios that do not completely encompass the risks associated with electronic device usage. For instance, during flight at any altitude, while it may seem like a blanket prohibition, specific regulations often distinguish between IFR and VFR conditions. Likewise, limitations such as only at night or when not using autopilot do not address the critical necessity of undisturbed navigation systems, which are paramount under IFR.