Which land cover type has the least area in united states

Urban area.

Explanation:

according to united state census 2010

forest area land present in United States is 46% of the total area.

wet lands is about 6% of the total area.

where as urban area is around 3% of the total  area present in the united states.

hence, the least area present in the united states is urban area which is about 3% of the total present area of the USA.

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.