The transfer function of an amplifier is given by

$A=\frac{A_0}{\{1+j\frac{}{{}_0}{\}}^2}$

where $A_0$ and ${}_0$ are positive constants and $A_0$ is $46$ dB $.$

What is the absolution value of the gain $($in dB $)$ for $={}_0?$

$40$ dB

$43$ dB

$46$ dB

$39$ dB

none of these