An aqueous solution of a salt X turns blood red on treatment with $SCN^{-}$ and blue on treatment with $K_4[Fe(CN)_6]$. $X$ also gives a positive chromyl chloride test. The salt X is :

Question

$\begin{array}{1 1} CuCl_2 \\ FeCl_3 \\ Cu(JNO_3)_2 \\ Fe(NO_3)_3 \end{array} $