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: __E__E__E 
Clue: A form of address for some royalty, it means calm & unruffled

SOLUTION: serene

PROBLEM: Category: WORLD HISTORY 
Clue: He completed vols. 2 & 3 of Karl Marx's "Das Kapital"

SOLUTION: friedrich engels

PROBLEM: Category: NAMES BY THE NUMBER 
Clue: Moe Howard, Larry Fine & Curly Howard

SOLUTION:
the three stooges