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

( A ) $FeCl_3$
( B ) $Fe(NO_3)_3$
( C ) $CuCl_2$
( D ) $Cu(NO_3)_2$