Which of the following functions is the inverse of itself ?

• A

  $\mathrm{f}\left(\mathrm{x}\right)=\frac{1-\mathrm{x}}{1+\mathrm{x}}$

• B

  $\mathrm{f}\left(\mathrm{x}\right)=5^{\log \mathrm{x}}$

• C

  $\mathrm{f}\left(\mathrm{x}\right)=2^{\mathrm{x}(\mathrm{x}-1)}$

• D

  None of these