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.

Category: THEY EAT THAT? 
Clue: A food stand by London's Petticoat Lane is called, & serves, "Jellied" this elongated fish
eel

Category: CHOOSE A "CIDE" 
Clue: The killing of cats
felicide

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

friedrich engels