I think B. The argument says that each person should be free to wear seat belts because he/she is allowed to take such a risk as long as nobody else is harmed as a result of him/her taking the risk.
A) does not even come close to weaken the argument
B) the right answer since it says that because of those people not wearing seat belts, the cost of car insurance for everyone
C) is off topic
D) does not offer any evidence for whether people not wearing seat belts harm others by their reckless act
E) This does not weaken the argument since again, it just shows that people not wearing seat belts harm themselves more than the people who do