TASK DEFINITION: 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.
PROBLEM: Category: ROCKS & MINERALS 
Clue: A mixture containing antimony is sprayed on canvas to render it this

SOLUTION: fireproof

PROBLEM: Category: IN THE PAST MILLENNIUM 
Clue: In 1066 this group conquered England

SOLUTION: normans

PROBLEM: Category: twentysomething 
Clue: To the closest mile, it's the length of an Olympic marathon

SOLUTION:
twenty-six