The intensity of sound wave while passing through an elastic medium falls down by 10% as it covers one metre distance through the medium. If the initial intensity of the sound wave was 100 decibels, its value after it has passed through 3 metre thickness of the medium will be
A. 70 decibel
B. 72.9 decibel
C. 81 decibel
D. 60 decibel
