An AI governance policy requires model owners to reassess AI risk when a 'trigger event' occurs. Which of the following would MOST appropriately constitute a trigger event requiring reassessment?

B is correct because expanding a model to serve a new customer segment with different demographics and risk profiles represents a material change in use case that can invalidate the original validation's findings. The model was validated for a specific population, and performance may differ substantially for a new segment. This is a classic trigger event for reassessment. Age of training data (A) may be relevant but is not inherently a trigger; what matters is whether it still represents the current population. Staff turnover (C) affects governance but not model validity directly. Consistent performance (D) supports maintaining the current risk assessment, not triggering reassessment.