If $x =\log_{0.1} 0.001, \; y = \log_9 81$, then $\sqrt{x -2\sqrt{y}}$ is equal to :

Question

( A ) $\sqrt{2} -1$
( B ) $\sqrt{3} -2$
( C ) $\sqrt{2} -2$
( D ) $3-\sqrt{2}$