Final answer:
Option (b), Roosevelt and many other American presidents aimed to express the importance of a unified nation. Through persuasive speeches and actions, they encouraged the American public's cooperation and confidence to face national challenges.
Step-by-step explanation:
Roosevelt tried to convey the idea that America was, and should continue to be, a unified nation. Through his actions and words, such as the fireside chats and phrases like "The only thing we have to fear is fear itself," he aimed to galvanize the American public, building support and cooperation to collectively address national crises. He emphasized the importance of public confidence, cooperation, and unity, framing his message around the concept of shared efforts and responsibilities to overcome economic depression and other issues.
Other presidents, like Woodrow Wilson, similarly sought national unity, especially during times of conflict like World War I, with campaigns like "America First" to promote a unified American identity over individual immigrant allegiances.
Later presidents, such as John F. Kennedy, would also invoke themes of national aspiration and unity. However, some, like Carter, were criticized for lacking the reassuring and galvanizing rhetoric that citizens expected based on Roosevelt's precedents. Overall, the underlying idea Roosevelt and many of his successors aimed to communicate was the importance of a unified populace focused on the common good during challenging times.