The line "And so, my fellow Americans: ask not what your country can do for you — ask what you can do for your country" serves to C. shift the subject of the text toward the audience by asking citizens to contribute to the public good and inspire civic action.
This line emphasizes the importance of individual responsibility and civic engagement, encouraging citizens to take an active role in the betterment of society rather than simply expecting government support. It captures the spirit of public service and collective action that Kennedy sought to promote during his presidency.