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.

[Q]: Category: "X" IN THE CITY 
Clue: Famous for temple ruins, this city on the site of Thebes has been called "The World's Greatest Open-Air Museum"
[A]: luxor


[Q]: Category: "R"RRRRR! 
Clue: Frank Gorshin played him on the small screen, Jim Carrey on the big
[A]: the riddler


[Q]: Category: FOOL'S ERRANDS 
Clue: Alchemists once searched for the philosopher's stone, said to transmute base metals into this substance
[A]:
gold