What happens to the atomic radius when an elctron is lost

It decreases.

Explanation:

Due to changes in the Coulombic force, the protons within the nucleus of the ion have a much easier time pulling at one fewer electrons. This way, the electrons are pulled closer to the center, causing the radius to decrease.

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.