Which of the following has the least electron affinity in $kJ\,mol^{-1}$?

Knowing the electron gain enthalpy values for $O \rightarrow O^{-}$ and $O \rightarrow O^{2-}$ as $-141 \ kJ \ mol^{-1}$ and $702 \ kJ \ mol^{-1}$ respectively,how can you account for the formation of a large number of oxides having $O^{2-}$ species and not $O^{-}$?
(Hint: Consider lattice energy factor in the formation of compounds).

Which of the following statements regarding electron affinity is correct?

The correct sequence of electron gain enthalpy of the elements listed below is
$A$. $Ar$ $B$. $Br$ $C$. $F$ $D$. $S$
Choose the most appropriate from the options given below:

Electron gain enthalpy values $(\Delta_{eg} H)$ (in $kJ \ mol^{-1}$) of elements $X$,$Y$ and $Z$ are $-349$,$-200$ and $-295$ respectively. $X$,$Y$ and $Z$ are respectively

Which electron affinity process would liberate the most energy?