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.

[Q]: Category: THE BRITISH ISLES 
Clue: Britain's oldest known scrap of material called this, sometimes identified as shepherd's plaid, dates from 250 A.D.
[A]: tartan


[Q]: Category: AMERICAN NOVELISTS 
Clue: "What is moral is what you feel good after and what is immoral is what you feel bad after", he wrote in 1932
[A]: ernest hemingway


[Q]: Category: OPEC 
Clue: This African nation of 150 million is the only member of OPEC that's also a member of the British Commonwealth
[A]:
nigeria