In this phrase, fire refers to which of the following? endeavors like this one energy, faith, and devotion lights of those who serve the light of our countrythe energy, the faith, the devotion which we bring to this endeavor will light our country and all who serve it—and the glow from that fire can truly light the world.

In President John F. Kennedy's Inaugural Address, January 20, 1961, fire refers to Energy, faith and devotion.

In Kennedy's Inaugural Address he first states that his victory is not the victory of a party but the victory of freedom and change. Then he says that the people of the United States are faced with the historic effort of defending freedom, and the energy, faith and devotion that they bring, will light their country and the whole world.

sentence lenght varies according to word choice.you select which word to use and that will require to use other expressions that collocate with the word chosen.sentence length will vary   according to the choice of words you make to express your ideas.  

excerpt from "the   daffodils" by william wordsworth