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.

[EX Q]: Category: NONFICTION 
Clue: This 1988 bestseller was subtitled "From the Big Bang to Black Holes"
[EX A]: a brief history of time

[EX Q]: Category: ORGANIZATIONS 
Clue: This service "Club" has a 4-way test of things they think, say & do, including "Will it be beneficial to all concerned?"
[EX A]: the rotary club

[EX Q]: Category: "I" DOCTOR 
Clue: The pancreas secretes this hormone in response to high levels of blood sugar
[EX A]:
insulin