Correct order of first I.P among following elements Be, B, C, N, O

Be−1s22s2;B−1s22s22p1;C−1s22s22p2;N−1s22s22p3;O−1s22s22p4. IP increases along the period. But IP of Be > B. Further IP of O < N because atoms with fully or partly filled orbitals are most stable and hence have high ionisation energy.