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: STAND BY YOUR MANNEQUIN 
Clue: In a magazine called The Show Window, this Oz creator dispensed advice on mannequins & creative display
l. frank baum

Category: THE HISTORY OF APRIL 9th 
Clue: 1959: NASA publicly introduces Messrs. Glenn, Shepard & the rest of this program's 7 astronauts
mercury

Category: THE TITANIC 
Clue: Gates prevented 700 of these passengers from getting up to the main deck, though they didn't stop Leo in the movie

third class