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: "M.C." 5 
Clue: Edgar Degas' style influenced that of this female American Impressionist
mary cassatt

Category: BUSINESS & INDUSTRY 
Clue: This package delivery firm was founded in 1907 as the American Messenger Company
ups

Category: FIREFIGHTING 
Clue: Red Adair mastered extinguishing oil & gas fires by setting off these to suck the oxygen from the blaze

explosions