(A)H3BO3− Hydrogen bonding Boron is attached to three O-atoms and each oxygen is bonded to one hydrogen, each such unit is H3BO3.
(B) AlCl3 - Dimeric form AlCl3 form dimer and exist as Al2Cl6.AlCl3 is an electron deficient compound, thus behave as Lewis acid.
(C) B3N3H6 - Inorganic benzene B3N3H6 (Borazine) is a polar inorganic cyclic compound, three BH units and three NH units alternate.
(D) BF3 - Back bonding The exchange of electrons between an atomic orbital on one atom and an antibonding orbital on another atom is known as back bonding.