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.

Category: police punishment 
Words: hearing, firstrate, alert, custody, fine
alert

Category: consumer product 
Words: shop, tools, happy, service, content
happy

Category: military rank 
Words: commander, private, fighter, boring, general

boring