If the last transponder inspection was performed on September 1, 2014, by when is the next inspection due?

The interval for transponder inspections is every 24 months, or two years. If the last inspection was conducted on September 1, 2014, adding two years brings the due date to September 1, 2016. However, regulations typically require that an inspection must be completed by the last day of the month in which the inspection is due. Therefore, the next inspection must be completed by September 30, 2016. This aligns with the option provided, which indicates September 30, 2016, as the correct due date for the next inspection.