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: AROUND THE HOUSE 
Clue: A silent butler is used to collect these during or after a meal
crumbs

Category: TRANSPORTATION 
Clue: In the 19th century Gustavus Swift developed this type of railway car to preserve his packed meat
refrigerator car

Category: J.R.R. TOLKIEN 
Clue: It's the third volume in the "Lord of the Rings" trilogy

the return of the king