Final answer:
Paragraphs 6-7 emphasize that the United States faced both negative and positive outcomes from WWII, becoming economically prosperous while also contending with various domestic issues.
Step-by-step explanation:
The paragraphs 6-7 contribute to the development of ideas in the text by illustrating that the United States experienced both negative and positive consequences from World War II. This can be seen in the fact that while the US emerged economically prosperous, with advancements in technology, a strong military, and a new role in international trade and banking, it also faced domestic challenges such as questions about women's roles in the postwar economy, the fate of New Deal programs, and wartime economic controls. The text also mentions the growth in population and industry during the pre-war period, setting the stage for America's future growth and capacity to become a world leader post-war.
In conclusion, the correct choice among the given options would be B, as it accurately reflects the dual impact of the war on the United States, which aligns with the content of paragraphs 6-7 and additional information provided in the text about the period after World War II.