Ionization energy increases in the order

The first ionization enthalpy values (in $kJ\,mol^{-1}$) of group $13$ elements are :

$B$	$801$
$Al$	$577$
$Ga$	$579$
$In$	$558$
$Tl$	$589$

How would you explain this deviation from the general trend?

The ionization potential of sodium is $5.48 \ eV$. The $I.P.$ of potassium is ............. $eV$

Match List-$I$ with List-$II$:

List-$I$ (Electronic configuration of neutral atom where $n=2$)	List-$II$ ($1^{st}$ Ionization Energy in $\text{kJ mol}^{-1}$)
$A. ns^2$	$I. 2080$
$B. ns^2np^1$	$II. 899$
$C. ns^2np^3$	$III. 800$
$D. ns^2np^6$	$IV. 1402$

Find the formula of the halide of a metal whose successive ionization energies are $10, 16, 25, 400, 500 \ eV \ mol^{-1}$ respectively $:-$

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: The first ionization enthalpy of $O$ is lower than that of $N$ and $F$.
Reason $R$: The loss of an electron from $O$ leads to a stable half-filled $p$ orbital.
In light of the above statements, choose the most appropriate answer from the options given below: