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: BRITISH AUTHORS 
Clue: His son Christopher said, my father "got to where he was by climbing upon my infant shoulders"
a.a. milne

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
beijing & lhasa

Category: PHILOSOPHY 
Clue: Nietzsche wrote, "Once you said 'God' when you gazed upon distant seas; but now I have taught you to say" this word

superman