Identify the incorrect order of first ionization energy.

Identify the incorrect order of first ionization energy is $Be<B<C$.

The sequence of Be, B, and C's ionization potentials is  $Be<B<C$  is false. Because the effective nuclear charge grows with time, causing an increase in the ionization potential from left to right.

 Be has a greater ionization potential than B. Be and B both have the electrical configurations $1{\mathrm{s}}^{2}2{\mathrm{s}}^2$and $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^1$ respectively. P electron removal uses less energy than s electron removal.

Hence, the option C is correct