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.

Category: MOZART & FRIENDS 
Clue: Mozart wrote a lovely motet for Venanzio Rauzzini, one of these specially treated singers
a castrato

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"
frost

Category: EDUCATION 
Clue: In 1836 he became president of Cincinnati College & published his 1st "Eclectic Reader"

william mcguffey