What must be ensured for edge transitions in braking systems?

In the context of edge transitions in braking systems, ensuring that each line has enough friction to stop the full load if one fails is critical for safety and effectiveness. This principle is rooted in the understanding that any failure in a line could create an unsafe situation. If one line were to fail, the remaining line must have sufficient friction and resistance to handle the entire load without causing excessive wear or risk of failure itself.

Having adequate friction allows the system to control the descent or hold the load securely, mitigating the potential dangers associated with edge transitions, such as abrupt movements or uncontrolled descents. This redundancy is a key component of safety in rescue operations, as it contributes to the overall reliability of the braking system under varying conditions that can be encountered during a rescue.

The other options do not address the critical aspect of load management and safety regarding edge transitions in this context. The need for balance and reliability across multiple lines is paramount, making option B the most effective strategy for ensuring safety in rope rescue operations.