Ionization potential is lowest for

The electronic configurations 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 $C$?

Which among the following elements has the lowest value of $IE_1$?

Which particle may be removed from a stable neutral atom with the least energy change?

Of the following isoelectronic ions,the one which has the lowest ionisation potential is

What is the correct order of the first ionization energy for $Li, Be, B,$ and $Na$?