The expression will be
$f = \overline{ \overline{( x \overline{y} )}(yz)} = \overline{( \overline{x}+y)(yz)} = \overline{ \overline{x}yz+yz } = \overline{(\overline{x}+1)(yz) } = \overline{1(yz)} = \overline{yz} = \overline{y}+\overline{z}$
The final expression only contains $y$ and $z$,
Therefore, answer will be (A) f is Independent of $x$.