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: animal 
Words: ant, walk, bike, fly, dangle
bike

Category: type of rigidity 
Words: unbending, unyielding, inflexible, firm, streamline
streamline

Category: chocolate food 
Words: tart, cookies, smear, rich, fudge

smear