To meet the requirement for the number of VDSs on board, what must be true about pyrotechnic VDSs?

For visual distress signals (VDS) to meet regulations for boating safety, pyrotechnic VDSs must be unexpired. This is crucial because expired signals may not function properly in emergency situations, which could jeopardize the safety of boaters in distress. The reliability of these devices is paramount, as they are designed to attract attention during emergencies, and using an expired device could fail to signal for help effectively.

Options related to size or visibility, while important in some contexts, do not apply specifically to the requirement for VDSs regarding being unexpired. Ensuring that the pyrotechnic VDSs are within their expiration dates is a critical safety requirement that directly affects their performance in emergencies.