The correct answer is C) weighed. The small passenger vessel regulations require that at each initial and subsequent inspection for certification, all carbon dioxide fire extinguishers aboard a vessel must be weighed. This ensures that the extinguisher contains the required amount of carbon dioxide, as specified by the manufacturer, to be fully effective in the event of a fire. Weighing the extinguishers is a simple and reliable way to verify that they are properly charged and ready for use. The other options are incorrect because: A) checking for pressure loss does not provide a complete assessment of the extinguisher's contents, B) discharging and recharging the extinguishers is not necessary at every inspection, and D) sending the extinguishers to an approved service facility is not required at each inspection.