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: BODY LANGUAGE 
Clue: When vou're idle or just plain bored, you do this with your pollex digits, literally or figuratively

A: twiddle your thumbs
****
Q: Category: 3-LETTER WORDS 
Clue: To udderly intimidate someone

A: cow
****
Q: Category: NONFICTION 
Clue: This 1988 bestseller was subtitled "From the Big Bang to Black Holes"

A:
a brief history of time
****