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 simplicity, answers should be in all lower cased letters.
PROBLEM: Category: OIL PAINTING 
Clue: This painting surface may be linen or cotton & is placed on a frame called a stretcher

SOLUTION: canvas

PROBLEM: Category: SCIENCE 
Clue: What you're "stuck with" boiling down collagen, softening it with hot water & letting it swell

SOLUTION: glue

PROBLEM: Category: WHAT'S ON TV? 
Clue: This Neil Patrick Harris sitcom is narrated through flashbacks from the future

SOLUTION:
how i met your mother