Where is a colon used in a formal buisness letter

Accepted is to fact as unproven is to

Modernist poets were concerned with many issues and used their poetry to express their concerns. which item from this list was not one of their concerns? a.corruption of traditional american values b.brutality of wwi c.the effects of the great depression d.crowded, crime-ridden city life e.alienation of the individual

In 3 sentences explain how ambrose bierce's use of foreshadowing or flashback influences "an occurence at owl creek bridge "