If $f:A\rightarrow B$, $3^{f(x)}+2^{-x}=4$ and $f(x)$ is bijection then the domain $A$ of $f(x)$ is ?

Question

$\begin{array}{1 1} (-2 ,\infty) \\ (-3, \infty) \\ (-1,1) \\ (-2,2) \end{array} $