In SONAR, we use :

Options

A. ultrasonic waves
B. infrasonic waves
C. radio waves
D. audible sound waves

Explanation

**Step-by-Step Solution:**

1. **Understanding SONAR**: SONAR stands for Sound Navigation and Ranging. It is a technology used to detect and locate objects underwater.

2. **Function of SONAR**: SONAR works by emitting sound waves and analyzing the echoes that return after bouncing off underwater objects. This helps in measuring the distance, direction, and speed of these objects.

3. **Types of Waves Used**: SONAR specifically utilizes sound waves. The options given are ultrasonic waves, infrasonic waves, radio waves, and audible sound waves.

4. **Identifying the Correct Type of Waves**:
- **Ultrasonic Waves**: These are sound waves with frequencies above the audible range (above 20 kHz) and are commonly used in SONAR because they can travel long distances in water.
- **Infrasonic Waves**: These are sound waves with frequencies below the audible range (below 20 Hz) and are not suitable for SONAR.
- **Radio Waves**: These are electromagnetic waves and are not used in SONAR.
- **Audible Sound Waves**: These are sound waves within the human hearing range (20 Hz to 20 kHz) and are not effective for underwater navigation.

5. **Conclusion**: Since SONAR uses sound waves that are above the audible range, the correct answer is ultrasonic waves.

**Final Answer**: In SONAR, we use ultrasonic waves.

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