Answer:
The collapse of the Old Kingdom was followed by decades of famine and strife.
The correct answer is A) building shelters.
The pioneers’ first priority was building shelters.
Life was difficult for pioneers who decided to leave their former lands and travel to the west in the time if US history called "the westward expansion." The Oregon Trail was also a difficult road to cross. Many people could complete it. Hunger was a major issue.
Pioneers had to build their shelters to endure climate conditions, clear the land for farming. However, the opportunity to have their own portion of land motivated many farjmers, former slaves, and immigrants.
The Santa Fe trail started in Independence, Missouri and ended in Santa Fe, New Mexico (hence the name, Santa Fe). Hope this helped!