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: DRAMA 
Clue: Sula & Helena are robotesses in this Karel Capek play
[A]: "r.u.r."


[Q]: Category: "TWO" 
Clue: It features Jefferson on the front & the signers of the Declaration on the back
[A]: two-dollar bill


[Q]: Category: MODERN OPERA 
Clue: This Hungarian composer wrote only one opera, the dramatic 1-act "Duke Bluebeard's Castle"
[A]:
bela bartok