The amount of. moisture in the air is highest when relative humanity is

Saturation is the maximum amount of water vapor in the air at an existing temperature and pressure. Air is said to be saturated at 100 percent relative humidity when it contains the maximum amount of moisture possible at that specific temperature. Dew point is the temperature when air reaches 100% relative humidity.

14,16 18 reacts with group

hydrocarbons are organic compounds that contain only hydrogens and carbons. they can be saturated (those which contain only carbon-carbon single bonds) or unsaturated (those which contain carbon-carbon double or triple bonds) in nature. hydrocarbons can undergo several reactions like substitution, elimination etc.  

on substituting one or more hydrogen atoms in hydrocarbon it results in the formation of haloalkane. as the halogen atoms are large compared to the carbon and hydrogen atoms, due to which the molecular weight increases and the bond become polar because of presence electronegative halogen atom and results in the increase in boiling point of the haloalkane.

thus, the correct option is (b) that is the boiling point of the new compound increases on substituting a hydrogen atom with a halogen in a hydrocarbon.