SONAR Waves Used:

Ultrasonic Waves:
- SONAR systems primarily use ultrasonic waves for underwater communication and navigation.
- These waves have frequencies higher than the audible range of human hearing, typically above 20 kHz.
- Ultrasonic waves can travel long distances underwater and provide accurate depth measurements and object detection.

Infrasonic Waves:
- Infrasonic waves have frequencies below the audible range of human hearing, typically below 20 Hz.
- These waves are not commonly used in SONAR systems due to their limited ability to travel through water and their lower resolution compared to ultrasonic waves.

Radio Waves:
- Radio waves are not used in traditional SONAR systems as they do not propagate well in water.
- Radio waves are typically used in radar systems for long-range detection and communication in the air and space.

Audible Sound Waves:
- Audible sound waves are not commonly used in SONAR systems as their frequencies are within the range of human hearing.
- Using audible sound waves can cause interference with marine life and other underwater activities.

In conclusion, ultrasonic waves are the most effective choice for SONAR systems due to their ability to travel long distances underwater, provide accurate measurements, and avoid interference with marine life.

A) ultrasonic waves