Which of the following is true about a zero decibel sound level

A) is nonsense
B) is just at the threshold of hearing
C) has zero amplitude
D) none of the above

B.
0dB sound level is 10^-12W/sq.m - about the threshold of hearing.

Decibel = 10 log(Intensity1/intensity2) = 20 log(Pressure1/Pressure2) {because intensity is proportional to the pressure squared.}
Now, If Intensity1 = Intensity2 or Pressure1 = Pressure2,
Then, decibel = 10 log 1/1 = 10 log1 = 10 *0 =0 decibel, Now think over it,
That is, both the Output and input in terms of intensity or pressure or wattage...
Decibel =0 decibel is the answer non of which matches with A) to D). Thank you.

b

C is the answer