Which statement best explains how the organizational structure of the passage helps develop the main idea?

When Alana first came to Timber Creek, things sure looked different than they do now. The only structures in town were canvas tents, and folks had to wait for supplies to come by wagon train. Once the railroad was built, supplies arrived much more quickly. A sawmill went up the following year, and people started building wooden homes and shops. Now, Timber Creek has a real paved road through the center of town.
A.
The chronological structure gives reasons and makes arguments in order to show how life in Timber Creek could be improved.
B.
The compare-and-contrast structure examines Alana's life before and after the sawmill was built in order to prove that wooden houses are superior to tents.
C.
The problem-solution structure identifies the difficulty of getting supplies in order to show how important the railroad is to Timber Creek.
D.
The chronological structure describes the changes that came to Timber Creek in order to show how the community has developed over time.