Which of the following metals forms more than one chloride?

Which of the following metal ions in their respective oxidation states forms a coloured compound?

In the following pairs,the one in which both transition metal ions are colourless is

Which of the following ions is coloured?

The correct statement$(s)$ about $Cr^{2+}$ and $Mn^{3+}$ is(are)
[Atomic numbers of $Cr = 24$ and $Mn = 25$]
$(A)$ $Cr^{2+}$ is a reducing agent
$(B)$ $Mn^{3+}$ is an oxidizing agent
$(C)$ Both $Cr^{2+}$ and $Mn^{3+}$ exhibit $d^4$ electronic configuration
$(D)$ When $Cr^{2+}$ is used as a reducing agent,the chromium ion attains $d^3$ electronic configuration

The lanthanide contraction is responsible for the fact that