I believe your answer would be Kennedy wanted to give an inspiring speech without being long-winded. Hope this helps!
A. Because an allusion is a reference to a known figure. All other sentences contain an allusion to famous musicians.
A legend is a caption, a title or brief explanation appended to an article, illustration, cartoon, or poster.
A key is an explanatory list of symbols used in a map, table, etc.
a. cyclical . if you look at the others its contributing to some sort of essay
C. seamus heaney .
Hope this helped!