Solution :Due to Hydrozen bonding Gauche conformation of `H_(2)N-CH_(2)-CH_(2)-NH_(2) " and " HO-CH_(2)-CH_(2)-F` are more stable than ANTICONFORMATIONS. In case of `CICH_(2)CH_(2)CI` on INCREASING temperature % of Gauche conformation increases. Hence dipole moment increases. In case of option (D) BOAT conformation is more stable.