Of the ions $Z{n}^{2+},N{i}^{2+}$  and $C{r}^{3+}$

(At.Nos Zn =30, Ni = 28, Cr = 24)

Only $Z{n}^{2+}$  is colourless and $N{i}^{2+}$  and $C{r}^{3+}$  coloured

All three are colourless

All three are coloured

Only $N{i}^{2+}$   is coloured and $Z{n}^{2+}$  and $C{r}^{3+}$  are colourless