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.

Q: Category: VITAMINS & MINERALS 
Clue: The name of this vitamin is from the Latin for "leaf" because leafy green vegetables are a good source

A: folic acid
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Q: Category: TRAINS 
Clue: As of 2006, you can take a 48-hr. ride between these 2 cities, with a stretch on the world's highest railroad

A: beijing & lhasa
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Q: Category: WORLD EVENTS 
Clue: The 3 people who did this most recently were Midori Ito, Muhammad Ali & Crown Prince Haakon of Norway

A:
lighting the olympic flame at the olympic games
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