In an aqueous solution of Fe (III) and $\left({\text{SCN}}^{-}\right)$, the equilibrium can be represented as follows: $\underset{\text{Pale\hspace{0.17em}yellow}}{{\text{Fe}}_{\left(\text{aq}\right)}^{\text{3+}}}\text{\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}+\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}\hspace{0.17em}}\underset{\text{Colourless}}{{\text{SCN}}_{\left(\text{aq}\right)}^{-}}\rightleftharpoons \underset{\text{red}}{{\left[\text{Fe}\left(\text{NCS}\right)\right]}_{\left(\text{aq}\right)}^{\text{2+}}}$ For this choose correct statements 

When KSCN is added to it there is no change in colour 

When oxalic acid is added, there is a decrease in red colour

When ${\text{HgCl}}_{2\left(aq\right)}$ is added the red colour disappears 

When ${\text{FeCl}}_{\text{3}}$is added to it there is no change in colour