How do molecules of butene form polybutene?

Polybutene exists in two isomeric forms depending on where the carbon double bond is positioned in the monomer molecule. If it is between the first and second carbon atoms in a linear molecule, then the chemically accurate name of the resulting polymer is polybutene-1.

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.