$\text{A.}$ $f(x)=x^2-2 x-1, g(s)=s^2-2 s-1$
$\text{B.}$ $f(x)=x-1, \quad g(x)=\frac{x^2-1}{x+1}$
$\text{C.}$ $f(x)=\sqrt{x^2}, \quad g(x)=\left\{\begin{array}{l}x, \quad x \geqslant 0, \\ -x, \quad x < 0\end{array}\right.$
$\text{D.}$ $f(x)=\sqrt{-x^3}, \quad g(x)=x \sqrt{-x}$
$\text{E.}$
$\text{F.}$