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: TRAVEL INDIANAPOLIS 
Clue: Union Station has a hotel that features these sleeping cars converted into hotel suites

SOLUTION: pullman cars

PROBLEM: Category: NAME THAT CENTURY 
Clue: President McKinley is assassinated

SOLUTION: the 20th century

PROBLEM: Category: WE'RE NO. 1 
Clue: Nicaragua was the first country to ratify this charter in 1945; the U.S. took another 3 weeks

SOLUTION:
u.n. charter