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: PHONING IT IN 
Clue: Reflecting the company's activities at its founding in 1885, it was the second "T" in AT&T
telegraph

Category: GEOLOGISTS 
Clue: In 1957 Sir Vivian Fuchs led the first crossing of this continent; it took 99 days
antarctica

Category: THE PLANETS 
Clue: This largest planet spins the most rapidly; its day is just 10 hours long

jupiter