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: GRAY MATTERS 
Clue: This hemisphere of the brain generally governs musical & artistic creativity

SOLUTION: right

PROBLEM: Category: RIVERS 
Clue: The mouth of this 2315-mile-long river lies in the Mississippi River 17 miles above St. Louis

SOLUTION: the missouri

PROBLEM: Category: I'M CONCERNED... 
Clue: This group, BBBS, concerns itself with helping children reach their potential by matching them with mentors

SOLUTION:
big brothers big sisters