How do APU components prevent the spread of fire?

The correct choice highlights the importance of titanium firewalls and thermal insulation in preventing the spread of fire within APU (Auxiliary Power Unit) components. Titanium firewalls serve as a robust barrier that can withstand high temperatures and prevent flames from migrating to adjacent areas. The use of thermal insulation further protects sensitive components and reduces heat transfer, thereby maintaining safe operating conditions.

In the context of APU safety, the combination of these materials plays a crucial role in containing any potential fire within the APU itself, thereby enhancing overall aircraft safety. The rigorous use of materials that can withstand intense heat is critical, as it reduces the risk of fire affecting other critical areas of the aircraft system and helps maintain operational integrity.