A. I think because Cadence, in music, the ending of a phrase, perceived as a rhythmic or melodic articulation or a harmonic change or all of these; in a larger sense, a cadence may be a demarcation of a half-phrase, of a section of music, or of an entire movement. (I am sorry if I am wrong )
Historical context can tell us important information about D. The author's purpose.
It suggests that Americans are in danger of losing their rights.
It predicts that the enemy will try to take away free speech.
It implies that the US will lose the war if Americans do not buy war bonds.