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 consistency, answers should be in all lower cased letters.
PROBLEM: Category: TRANSPORTATION 
Clue: In the 19th century Gustavus Swift developed this type of railway car to preserve his packed meat

SOLUTION: refrigerator car

PROBLEM: Category: MUSICAL GENRES 
Clue: This subgenre of metal can also mean "to beat savagely"

SOLUTION: thrash

PROBLEM: Category: IT'S "MAY"! 
Clue: Named for the festival once held there, it's a district of Central London

SOLUTION:
mayfair