Which one of the following order is correct for the first ionisation energies of the elements?

First ionisation energy increases in a period. Thus, the first IE of the elements of the second period should be as follows $\mathrm{Be} < \mathrm{B} < \mathrm{N} < \mathrm{O}$ But in practice, the elements do not follow the above order. The first IE of these elements is $\mathrm{B} < \mathrm{Be} < \mathrm{O} < \mathrm{N}$ The lower IE of $\mathrm{B}$ than that of $\mathrm{Be}$ is because in $\mathrm{B}$ $\left(1 s^2, 2 s^2 2 p^1\right)$, electron is to be removed from $2 p$ which is easy while in $\operatorname{Be}\left(1 s^2, 2 s^2\right)$, electron is to be removed from $2 s$ which is difficult. The low IE of $\mathrm{O}$ than that of $\mathrm{N}$ is because of the half-filled $2 p$ orbitals in $\mathrm{N}\left(1 s^2, 2 s^2 2 p^3\right)$.