The correct answer is a. true.
However, if federal law prohibits dealers and repair shops to directly disable the mechanism since 1998, under special circumstances, the National Highway Traffic Safety Administration (NHTSA) in the U.S can grant permission to do so, or set up an airbag on/off switch for the passenger side.
Being medically unable to keep a distance of at least 25cm from an airbag compartment, or a lack of weigh sensors in the vehicle automatically disabling the airbag for children or small adult under five feet five inches can be counted as fair reasons.