How many handbrakes must be applied during an evacuation?

The requirement to apply a sufficient number of handbrakes during an evacuation is based on ensuring the safety and stability of the train during an emergency situation. By applying an adequate number of handbrakes, the risk of the train rolling or moving unintentionally is minimized. This approach allows for flexibility, as the exact number needed can vary depending on the specific circumstances of the train's configuration, the number of cars involved, the gradient of the track, and other safety considerations.

The choice for a sufficient number emphasizes the importance of assessing the situation rather than adhering to a fixed number. This adaptability is crucial in emergency management within rail operations, as it accounts for different scenarios that may arise during an evacuation.

Other options specify a static number of handbrakes, which may not appropriately address the varied complexities of a real evacuation scenario. Therefore, understanding that applying a sufficient number of handbrakes accounts for these factors illustrates the correct approach to ensuring passenger safety during evacuation procedures.