What emergency frequencies are monitored by all ATS units?

The option that identifies the emergency frequencies monitored by all Air Traffic Service (ATS) units correctly is 121.5 and 243.0. These frequencies are designated for emergency communications in aviation.

121.5 MHz is the international distress frequency for civil aviation, widely recognized and used by aircraft in distress situations to communicate with air traffic control or other aircraft. It is monitored continuously by ATC facilities and also by aircraft nearby, ensuring that any distress call is heard and responded to promptly.

243.0 MHz is the emergency frequency used primarily by military aviation but also serves as an emergency frequency for civil aviation. While it may not be utilized as frequently as 121.5 in civil operations, it is still an essential frequency that military and certain emergency services monitor.

These frequencies are critical for safety in aviation, allowing pilots experiencing emergencies to communicate effectively with air traffic control and nearby aircraft regardless of altitude or location.