Which of the following electrons should have the highest value of ionisation energy (for the same value of the principal quantum number)?

The first ionization potentials in electron volts $(eV)$ of nitrogen and oxygen atoms are respectively given by:

Which of the following is not the correct increasing order of ionisation energy?

The ionization energy of boron is less than that of beryllium because

The correct order of ionisation energy for comparing carbon,nitrogen,and oxygen atoms is:

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: