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.

Q: Category: SEX CHANGES 
Clue: Don't let the pearls fool you, these lady bivalves can change into males when it suits them

A: oysters
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Q: Category: GOING WIRELESS 
Clue: Thanks to firms like Pegaso & Telemex, this country now has more cellular users than fixed line customers

A: mexico
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Q: Category: EASY MOLECULAR BIOLOGY 
Clue: Linus Pauling used X-ray crystallography to study the patterns of keratin in this body part

A:
hair
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