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: bus, leap, spider, run, fly
bus

Category: employment activity 
Words: ban, fire, empower, sack, ground
ground

Category: police punishment 
Words: fine, prime, alert, ticket, wispy

alert