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: employment activity 
Words: pay, instruct, heat, fire, scold

Answer: heat


Question: Category: boats 
Words: lifeline, stern, fold, deck, rudder

Answer: fold


Question: Category: elements 
Words: air, earth, hire, fire, inferno

Answer:
hire