Why do cars tires need more air in the winter then in the summer?
a) temperature is lower so tires expand
b) temperature is lower so tires contract
c) temperature is lower so the air inside the tires expand
d) temperature is lower so the air inside the tires contracts

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.