Final answer:
The conclusion that economic improvements in the South would be secondary to the need for progressive political change is the best supported by the provided texts. The texts highlight the South's economic potential and the necessity for social progress and better infrastructure for a true transformation.
Step-by-step explanation:
The best conclusion that can be drawn from multiple portions of both texts is b) That economic improvements would be secondary to progressive political change that needed to occur in the South. The texts reveal a multifaceted perspective on the South's development, highlighting not only the economic potential due to natural resources and inexpensive labor but also underlining the necessity of social progress, like greater democracy, infrastructural improvements such as railroads, and educational and personal freedoms that were more prevalent in the North.
The texts depict the South's economic prospects optimistically yet acknowledge the importance of progressive changes beyond mere economic improvement. The Southern economy was heavily reliant on a few crops and suffered from inadequate infrastructure and political systems, while the North invested in industry and valued free labor and social mobility - factors leading to its economic growth and appeal to immigrants and African Americans seeking better opportunities and personal freedoms.