If $x=log \, t $ and $y =\frac{1}{t^2}, $ then $\frac{d^2y}{dx^2}$ is :

$\frac{2}{t^2}$ $\frac{4}{t^2}$ $-\frac{1}{t}$ $-\frac{4}{t^2}$

$\frac{4}{t^2}$