$Fe{Cl}_3$ gives blood red colour with ${NH}_{4}SCN$. If $H_{2}S$ gas is passed and filtered then filtrate does not give red colour with ${NH}_{4}SCN$.

It is due to the presence on:

The correct option is B ${\left[Fe\right(SCN\left)\right]}^{2+}$
$Fe{Cl}_3$ on reacting with ${NH}_{4}SCN$ gives complex ion ${\left[Fe\right(SCN\left)\right]}^{2+}$ which is of red colour
$Fe{Cl}_3$ while reacting with $H_{2}S$, gives $Fe{Cl}_2$ which is not reacting with ${NH}_{4}SCN$. So, no colour is obtained.