At 298 K, the Ksp value of $Fe{\left(OH\right)}_3$ in aqueous solution is $3.8\times {10}^{-38}$. The solubility of $F{e}^{3+}$ions will increase when.

According to La-Chatelier principle.

$Fe {\left(OH\right)}_3\to F{e}^{{+3}^{ } }+3O{H}^{-}$

$H^{+}+O{H}^{-}\to H_{2}O$

According to the given equation as OH^- concentration decreases reaction proceeds forward so Fe³⁺ concentration increases and the solubility increases.
Hence the right answer is(C) pH is decreased.