Which block element from the following are known as transition elements?

Why is the $E^{\Theta }$ value for the $Mn^{3+}/Mn^{2+}$ couple much more positive than that for $Cr^{3+}/Cr^{2+}$ or $Fe^{3+}/Fe^{2+}$? Explain.

Which of the following cations in their given oxidation states forms colored compounds?

Assertion : Transition metals show variable valency.
Reason : Transition metals have a large energy difference between the $ns^2$ and $(n-1)d$ electrons.

The magnetic moments for $Ti^{2+}$,$V^{3+}$,and $Ni^{2+}$ are respectively:

Which pair of metal ions in their respective oxidation states forms colourless compounds?