What must aircraft slides at emergency exits be able to withstand?

Aircraft slides at emergency exits are designed to provide a safe and efficient means for evacuating passengers during an emergency. One of the critical factors in their design is their ability to withstand environmental conditions, including wind speeds. The correct choice highlights that aircraft evacuations can occur in various weather conditions, and the slides must remain operational and safe even when subjected to wind speeds up to 25 knots. This ensures that passengers can effectively utilize the slides without risk of being displaced or encountering additional hazards during high winds.

In contrast, while the other options might describe conditions that are important for different aspects of aircraft safety and emergency response, they do not pertain directly to the primary function of the emergency slides. For instance, slides do not need to support heavy cargo loads, as they are specifically meant for passenger evacuation. Additionally, they are not constructed to resist the presence of flammable materials in the same way that other safety measures would be applied within the aircraft. Similarly, while emergency vehicles are important in an overall emergency management scenario, the slides themselves are not designed to accommodate the travel of these vehicles. Thus, the focus is placed on the environmental durability of the slides in the specific context of human evacuation during emergencies.