( A ) $B < C < N < O$ Increasing first ionisation enthalpy
( B ) $Li < Na < K < Rb$ : Increasing metallic radius
( C ) $I < Br < F < Cl$ : Increasing electron gain enthalpy (with negative sign)
( D ) $Al^{3+} < Mg^{2+} < Na^+ < F^-$ : Increasing ionic size