Given a category and a set of five words, find the word from the set that does not belong (i.e. is the least relevant) with the other words in the category. Words are separated by commas.
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Question: Category: personal characteristic 
Words: ethical, tropical, unflappalbe, cool, optimist

Answer: tropical


Question: Category: type of sandwich 
Words: clan, lettuce, bacon, club, submarine

Answer: clan


Question: Category: computers 
Words: document, hardware, file, space, fax

Answer:
fax