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: chocolate food 
Words: cake, fudge, rich, invent, cream
invent

Category: police punishment 
Words: probation, suspension, jail, fine, attractive
attractive

Category: geographical property 
Words: flat, horizontal, mansion, hill, mountain

mansion