What must be designed for the specific evolution to be performed?

The correct answer focuses on the necessity of designing exterior props specifically for the evolving training scenario. When conducting live fire training, it is crucial that exterior props are tailored to the specific needs and conditions of the training exercise. This ensures that they accurately depict real-world firefighting situations, allowing trainees to engage in practical, hands-on learning.

Exterior props serve multiple purposes, such as simulating various types of structures or environments that firefighters may face. The customization of these props ensures they provide realistic challenges and hazards, ultimately enhancing the effectiveness of the training exercise. Additionally, having exterior props designed for the evolution helps ensure safety, as they can be built with fire-resistive materials and in configurations that promote effective training without undue risk to participants.

While interior props, training protocols, and fuel types are important considerations in the context of live fire training, the direct correlation between exterior props and the specific scenarios that trainees will encounter makes the design of these props a key element in preparing for successful evolutions.