Read this excerpt from The Great Fire. Schaffer's first signal went out at 9:30. Several minutes later, Schaffer realized his mistake and ordered Box 319 struck. This was still seven blocks away from the O'Learys', but close enough that firefighters could see the flames and alter their course. Unfortunately, Schaffer's young assistant, William J. Brown, stubbornly refused to strike Box 319, saying he was afraid it would confuse the situation. Brown was so stubborn about his decision that even after the fire he was able to write arrogantly in a letter that "I am still standing the watch that burned Chicago."

These errors had two fatal consequences. The most obvious was that a number of engines and dozens of firefighters were sent on a wild-goose chase and did not get to the fire for many minutes. More critical is that it kept fire companies located near De Koven Street in their stations. Several had seen the eerie, dancing glow beyond the rooftops near them and, even without official notice from Schaffer, prepared to respond. When they heard Box 342 rung, however, they assumed the fire was out of their territory and unhitched the horses. Only two fire companies were not fooled by the misleading alarm.

How does the structure of this excerpt illustrate the central idea that a series of individual mistakes contributed to the spread of the blaze?

by comparing and contrasting different people’s decisions and abilities
by comparing and contrasting the most effective firefighting techniques
by clearly explaining the reasons for the misleading alarm and its impact
by clearly explaining the reasons the fire started and the way it was put out