The first ionisation enthalpies (in $\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$) of the second-period elements are $\mathrm{Li}$ 520, $\mathrm{Be}$ 899, $\mathrm{B}$ 801, $\mathrm{C}$ 1086, $\mathrm{N}$ 1402, $\mathrm{O}$ 1314, $\mathrm{F}$ 1681, $\mathrm{Ne}$ 2081. Select the correct statements.

1. A${\Delta }_i{H}_1(\mathrm{B})>{\Delta }_i{H}_1(\mathrm{Be})$
2. B${\Delta }_i{H}_1(\mathrm{Ne})-{\Delta }_i{H}_1(\mathrm{Li})=1561$
3. C${\Delta }_i{H}_1(\mathrm{F})/{\Delta }_i{H}_1(\mathrm{Li})$ is greater than 3
4. DExactly two elements ($\mathrm{B}$ and $\mathrm{O}$) have a lower value than the element just before them