The correct option is A L = k log I
Loudness of the sound depends on its intensity, but loudness is not same as intensity. The loudness L and intensity I is given as, L = k log I where k is a constant of proportionality. Loudness increases with the increase in intensity, but not in the same proportion.
Taking k = 1, the sound level is written as
L = 10 log10 (I1/I0 ) dB