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.

[EX Q]: Category: HOMOPHONES 
Clue: A caustic substance in soap, or an untruth
[EX A]: lye/lie

[EX Q]: Category: SONGS 
Clue: The title song in an Elvis film, it was written for the 1937 Bing Crosby film "Waikiki Wedding"
[EX A]: blue hawaii

[EX Q]: Category: THE 18th CENTURY WORLD 
Clue: In 1776 this South American city was made the capital of the new Viceroyalty of the Rio de la Plata
[EX A]:
buenos aires