Which of the following elements has the highest first ionization enthalpy?

Which of the following orders of ionization energy is correct?

The elements of Group $13$ with highest and lowest first ionisation enthalpies are respectively$:$

The electronic configuration of elements $A, B$ and $C$ are $[He] 2s^1, [Ne] 3s^1$ and $[Ar] 4s^1$ respectively. Which one of the following orders is correct for the first ionization potentials (in $kJ \ mol^{-1}$) of $A, B$ and $C$?

Assertion $(A)$: First ionisation enthalpy of oxygen is less than that of nitrogen.
Reason $(R)$: Atoms with half-filled or completely filled orbitals are less stable.
The correct option among the following is:

The decreasing order of the ionisation potential in the following elements is