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

Category: employment activity 
Words: pay, instruct, heat, fire, scold
heat

Category: police punishment 
Words: fine, flyaway, firstrate, prison, level

level