(d)
The given expression of $\frac{1}{{(4 - 3x)}^{\frac{1}{2}}}$ can be rewritten as
$4^{\frac{- 1}{2}}\left( 1 - \frac{3}{4}x \right)^{\frac{- 1}{2}}$ and it is valid only when $\left| \frac{3}{4}x \right| < 1$
$\Rightarrow \ - \frac{4}{3} < x < \frac{4}{3}$