Which one of the following is a different pair?

Given below are two statements:
Statement $I$: The second ionisation enthalpy of $Na$ is larger than the corresponding ionisation enthalpy of $Mg$.
Statement $II$: The ionic radius of $O^{2-}$ is larger than that of $F^{-}$.
In the light of the above statements, choose the correct answer from the options given below.

Which of the following orders is correct?

$A, B$,and $C$ are hydroxy-compounds of the elements $X, Y$,and $Z$ respectively. $X, Y$,and $Z$ are in the same period of the periodic table. $A$ gives an aqueous solution of $pH < 7$. $B$ reacts with both strong acids and strong alkalis. $C$ gives an aqueous solution which is strongly alkaline.
Which of the following statements is / are true?
$I$: The three elements are metals.
$II$: The electronegativities decrease from $X$ to $Y$ to $Z$.
$III$: The atomic radius decreases in the order $X, Y$,and $Z$.
$IV$: $X, Y$,and $Z$ could be phosphorus,aluminium,and sodium respectively.

Nitrogen has positive electron gain enthalpy whereas oxygen has negative. However,oxygen has lower ionisation enthalpy than nitrogen. Explain.

Which of the following is the correct order of $I.E.$ (Ionization Energy)?