Which transition series includes elements $Co$ and $Mo$ respectively?

The correct statement about iron includes:
$I$) The highest oxidation state of iron is $+ 6$ in $K_2FeO_4$.
$II$) The iron shows $+ 2$ oxidation state with six electrons in the $3d$ orbitals.
$III$) The common oxidation state of iron is $+ 3$ with five unpaired electrons in the $3d$ orbital.

$Cr^{2+}$ has a magnetic moment same as that of

The transition elements have a characteristic electronic configuration which can be represented as:

Which of the following compounds is colored?

Elements of $d$-block are called