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: emotional status 
Words: left, emotional state, sad, emotional upsets, down

Answer: left


Question: Category: ocean 
Words: current, data sets, main, sea, wave

Answer: data sets


Question: Category: boats 
Words: head, sail, apron, crew, deck

Answer:
apron