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: FAMOUS PAIRS 
Clue: Now meaning nearly identical, these 2 names were applied to rivals Handel & Bononcini in a 1720s British verse

SOLUTION: tweedledum & tweedledee

PROBLEM: Category: THE 19th CENTURY 
Clue: 1853 purchase that brought the contiguous U.S. about up to its present area

SOLUTION: the gadsden purchase

PROBLEM: Category: THE SEA'S BOUNTY 
Clue: This shellfish of the family Mytilidae needs its beard removed, a little steaming & yum!

SOLUTION:
mussels