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.

Category: TV BEFORE & AFTER 
Clue: Jack Bauer saddles up & joins 3 friends bringing about the end of the world
24 horsemen of the apocalypse

Category: ANCIENT ROME 
Clue: This church faced periodic persecution for 300 years, until Constantine's conversion
christian church

Category: RECENT SPACE NEWS 
Clue: Of the 2 of these, NASA said Opportunity was "looking great", but Spirit had "dirty solar panels"

the mars rovers