This question is a little weak in that the OA does not have to be true given what is said in the passage.

Which of the following inferences is best supported by the passage above?

A) Prior to the "Click It or Ticket" law, motorists could not be stopped simply for not wearing a seat belt.

The passage says that "under the new law" motorists can be stopped even if an additional driving infraction has not been committed. From this I guess one is suppose to infer that prior to the passage of the new law motorists could not be stopped unless an additional infraction had been committed.

The truth is, however, that the prompt does not say anything that confirms that prior laws did not allow for stopping of motorists who had not committed infractions other than not wearing seatbelts. For all we know earlier laws also allowed for the stopping of motorists who had not committed infractions other than not wearing seatbelts. So the OA to this question would NOT be considered a logical inference on the actual GMAT.

In other words, while what A says is likely to be true, generally the correct answer to an official question will say something that MUST be true given what is said in the prompt.

B) The "Click It or Ticket" law violates current search and seizure laws.

While some argue that rights are violated by the law, search and seizure laws are not mentioned.

C) Laws similar to "Click It or Ticket" have effectively reduced traffic fatalities in a number of states.

Nothing in the passage suggests that other states even have such laws.

D) The previous seatbelt laws were ineffective in saving lives.

It may be the case the the previous seatbelt laws saved some lives even if the previous laws did not save as many lives as the new law is expected to save.

E) Law enforcement groups, rather than citizens groups, should determine how to best ensure the safety of motorists.

Two sides of the argument are presented without anything in the passage supporting the idea that law enforcement groups should determine how to be ensure safety.

So the best answer is A, although this question does not accurately represent how official inference questions work.