Which element has the maximum ferromagnetic character?

Observe the following statements:
$a$) The basic strength of $Lu(OH)_3$,$Gd(OH)_3$ and $Ce(OH)_3$ follows the order: $Ce(OH)_3 > Gd(OH)_3 > Lu(OH)_3$
$b$) $O^{2-}$,$N^{3-}$,$F^{-}$ and $Na^{+}$ are isoelectronic species
$c$) The sizes of $Zr$ and $Hf$ are approximately the same
The correct statements are:

Which of the following gaseous ions has the maximum number of unpaired electrons?

Which of the following metal ions will have the maximum number of unpaired electrons?

Which elements of the first transition series have higher ionization enthalpy values than their neighboring elements?

Which of the following alloys is used to construct marine condenser tubes of ships?