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: EUROPEAN CAPITALS 
Clue: Although capital of its country, it is not the capital of the province in which it's located, nor is it the seat of government
amsterdam

Category: U.S. GEOLOGY 
Clue: This 800-mile-long feature was discovered & named by Andrew Lawson

san andreas fault