The variability of oxidation states in transition elements arises from the incomplete filling of d orbitals and the participation of both $(n-1)d$ and $ns$ electrons in bonding. The number of oxidation states is related to the number of electrons available to be lost or shared.

1. Analyze Configurations:

• $3d^3 4s^2$ (Vanadium): Can lose up to 5 electrons ($3+2$). Exhibits oxidation states up to +5.
• $3d^5 4s^1$ (Chromium): Can lose up to 6 electrons ($5+1$). Exhibits oxidation states up to +6.
• $3d^5 4s^2$ (Manganese): Can lose up to 7 electrons ($5+2$). It has the maximum number of unpaired electrons in the 3d subshell paired with the 4s electrons. Manganese exhibits the largest number of oxidation states in the 3d series, ranging from +2 to +7 .
• $3d^2 4s^2$ (Titanium): Can lose up to 4 electrons ($2+2$). Exhibits oxidation states up to +4.

2. Conclusion: The configuration $3d^5 4s^2$ corresponds to Manganese, which shows the maximum number of oxidation states.