Ultrasonic waves are used in sonar with greater advantage, because they:

CONCEPT:

• Ultrasonic waves are the sound waves with frequencies higher than the upper audible limit of human hearing.
  • They have a short wavelength.
• SONAR: It a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, communicate with or detect objects on or under the surface of the water
  • SONAR stands for ‘Sound Navigation and Ranging.’
  • SONAR is based on the principle of echo.
  • Sonar is often used as a measurement of acoustic location and echo characteristics of the target object in the water.

EXPLANATION:

• The ultrasonic waves have short wavelengths and high frequencies.
• Due to the short wavelengths, it will travel greater distances with less diffraction. But the ordinary sound can't travel long distances without diffraction.
•  Also, the ultrasonic waves can't be heard by humans so there will not be any effect of noise also. That's why Ultrasonic waves are used in sonar with greater advantage. So option 3 is correct.