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: boats 
Words: check, stern, hull, galley, deck

Answer: check


Question: Category: elements 
Words: ban, fire, combustion, ground, flame

Answer: ban


Question: Category: computers 
Words: file, format, correspondence, keys, firewall

Answer:
correspondence