TASK DEFINITION: You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.
PROBLEM: Category: AMERICAN POETRY 
Clue: In "Stopping by Woods on a Snowy Evening", he wrote that he had "promises to keep, and miles to go before I sleep"

SOLUTION: frost

PROBLEM: Category: SHAKESPEARE 
Clue: "As You Like It" is partially set in the forest of this

SOLUTION: arden

PROBLEM: Category: POPES NAMED GREGORY 
Clue: In September 1376, Gregory XI moved the papacy from this city back to Rome

SOLUTION:
avignon