Major fires present the threat of wall collapse if the building was built during which era?

The correct choice identifies the Founders' Era as a time when building practices did not adhere to modern fire safety standards. During this period, construction often involved materials and methods that lacked the structural integrity and fire-resistant characteristics seen in later building designs. As a result, buildings from this era are more susceptible to collapse during major fires due to inadequate bracing and support systems.

In comparison, the Industrial Era introduced advancements in building materials, such as steel and reinforced concrete, which improved structural resilience. The Modern Era continued this trend, significantly enhancing fire safety codes and design practices to prevent structural failures. The Post-Modern Era further refined these practices, focusing on a combination of aesthetics and safety, particularly in high-rise buildings.

Thus, the vulnerability of structures from the Founders' Era to collapse in the event of a major fire demonstrates the significance of historical construction techniques and the evolution of fire safety standards over time.