The aqueous solution containing which one of the following ions...

$$\begin{aligned} & { }_{21} \mathrm{Sc}=1 s^2, 2 s^2 2 p^6, 3 s^2 3 p^6 3 d^1, 4 s^2 \\ & \text{ So, } S c^{3+}=1 s^2, 2 s^2 2 p^6, 3 s^2 3 p^6\end{aligned}$$ (It is colourless due to absence of unpaired electrons in $d$-stubshell) $$\begin{aligned} & { }_{26} \mathrm{Fe}=1 s^2, 2 s^2 2 p^6, 3 s^2 3 p^6 3 d^6, 4 s^2 \\ & \mathrm{Fe}^{2+}=1 s^2, 2 s^2 2 p^6, 3 s^2 3 p^6 3 d^6\end{aligned}$$ (It is coloured due to presence of four unpaired electrons in $d$-subshell.) $\begin{gathered}{ }_{22} \mathrm{Ti}=1 s^2, 2 s^2 2 p^6, 3 s^2 3 p^6 3 d^2, 4 s^2 \mathrm{Ti}^{3+}=1 s^2, 2 s^2 2 p^6, 3 s^2, 3 s^6 3 d^1\end{gathered}$ (It is coloured due to presence of one unpaired electron in $d$-subshell). $$\begin{aligned} & 25 \mathrm{Mn}=1 s^2, 2 s^2 2 p^6, 3 s^2 3 p^6 3 d^5, 4 s^2 \\ & \mathrm{Mn}^{2+}=1 s^2, 2 s^2 2 p^6, 3 s^2 3 p^6 3 d^5\end{aligned}$$ (It is coloured due to presence of five unpaired electrons in $d$-subshell)