Which of the $3d$ series of the transition metals exhibits the largest number of oxidation states and why?

(N/A) $Mn$ $(Z=25)$ has the electronic configuration $[Ar] 3d^{5} 4s^{2}$.
$Mn$ possesses the maximum number of unpaired electrons in the $d$-subshell ($5$ electrons) and $2$ electrons in the $4s$ orbital.
Due to the availability of these $7$ electrons for bonding,$Mn$ exhibits the largest number of oxidation states among the $3d$ transition metals,ranging from $+2$ to $+7$.