A/an tells us more about a noun or pronoun and must be placed directly before or directly after the noun or pronoun it refers to.

What does the line rage, rage against the dying of the light from the poem "do not go gentle into that good night" have in common with the line ride the six hundred from the poem "the change of the light brigade? "a. they end each stanzab. they are repetitious linesc. they end a sestetd. they begin an octave