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 consistency, answers should be in all lower cased letters.

[Q]: Category: EPITAPHS 
Clue: "Truth and history.  21 men.  The boy bandit king -- he died as he had lived"
[A]: billy the kid


[Q]: Category: MUSICAL GENRES 
Clue: This subgenre of metal can also mean "to beat savagely"
[A]: thrash


[Q]: Category: WEIGHTS & MEASURES 
Clue: If a gigawatt you see, this is the number of watts you get
[A]:
a billion