Which statement applies to electronegativity? electronegativity increases across a period. all atoms with the same number of electron shells have equal electronegativities. electronegativity is the amount of energy required to remove an electron from a gaseous atom. electronegativity increases down a group.

Electronegativity increases across a period.  

Explanation:

Electronegativity is defined as ability of an atom to attract shared pair of electrons in a bond toward itself.

Electronegativity increases across the period because when we move across the period from left to right numbers of protons and electrons are increased. By increase in number of protons ,nuclear charge also increases due to which electrons present in an atom are strongly attracted towards the nucleus. And due to presence of strong nuclear charge shared pair of electrons in a bond are also attracted towards nucleus of an electronegative atom.

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.