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

Answer: ban


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

Answer: fold


Question: Category: nutritional value 
Words: calcium, big, fat, absorption, heavy

Answer:
absorption