If the halogen atom is the same type in all the given alkyl halides, the boiling point of a compound increases on the increase of addition of alkyl groups. The attractions between the molecules and electrons get stronger as their number and size increase. Hence the higher the molecular weight of the alkyl halide, the higher the boiling point. The increasing order of boiling points of the given compounds are 1-Bromoethane < 1-Bromopropane < 1-Bromobutane < Bromobenzene. The correct option is (iv).