What strategy does Francis Scott Key use to develop the "glory" of the American flag?

He was inspired by the sight of a lone U.S. flag still flying over Fort McHenry at daybreak, as reflected in the now-famous words of the “Star-Spangled Banner”: “And the rocket's red glare, the bombs bursting in air, Gave proof through the night that our flag was still there.”

The answer is d.  the north had organized schools, whereas the south had few organized schools.