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: recruit, replace, sack, heat, fire

Answer: heat


Question: Category: shady activities 
Words: cookies, wrongful, fudge, smuggled, smear

Answer: cookies


Question: Category: corporate 
Words: unyielding, synergy, sustainability, united, firm

Answer:
unyielding