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.

Category: LET'S FOOL AROUND! 
Clue: "A Fool in Love" was the first big hit for this couple known for their stormy marriage & their "Revue"
ike & tina turner

Category: U.S. ENDANGERED SPECIES 
Clue: It's not only the chinook; the sockeye species of this fish is endangered also
salmon

Category: GUNS 
Clue: Napoleon was the first to mass artillery in a "Grande" or "Big" one of these; we're positive it was a negative for the enemy

a battery