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: ENGLISH 
Clue: Group of 4 letters that sounds different within words for done, exhaustive, hack, idea, branch & coarse
\"o-u-g-h\"

Category: SIGNS & SYMBOLS 
Clue: Created in 1970 & made up of 3 arrows, the universal symbol for this was based on the Mobius strip
recycling

Category: AMERICAN ARTISTS 
Clue: From 1919 to 1924, this artist taught art in the public schools of Cedar Rapids, Iowa

grant wood