An underwater sonar source operating at a frequency of 60 kHz directs its beam towards the surface. If velocity of sound in air is 330m/s, wavelength and frequency of the waves in air are

• A. 5.5mm, 60 kHz
• B. 5.5mm, 30 kHz
• C. 5.5mm, 30 kHz
• D. 5.5mm,80 kHz