Final answer:
The reason the author included information about America's transformation between 1850 and 1900 is to show that the changing nation needed new solutions to new problems, emphasizing the evolving challenges and the need for the Progressive Era reforms. option 3
Step-by-step explanation:
The inclusion of information about how America in 1850 differed significantly from America in 1900 likely serves to highlight the evolving challenges the country faced during that period. With the backdrop of economic hardships, including the Depression of 1893, and the rise and fall of the Populist movement, such context emphasizes the necessity for new solutions to address the rapidly changing national landscape. By the time of the Progressive Era, there was a clear recognition that the problems of a modernizing America required new strategies and leadership. Among the provided options, the most fitting reason for the inclusion of this historical transformation could be to show that a changed America needed new solutions to its problems (Option 3). This rationale aligns with the Progressive Era's push for reforms to cope with the effects of industrialization, urbanization, and political corruption that emerged as America transitioned from a rural to an increasingly industrial and urban society.