Given a set of five words, generate the word from the set that does not belong (i.e. is the least relevant) with the other words. Words are separated by commas.

[Q]: fire, hire, heat, inferno, earth
[A]: hire


[Q]: forward, opposite of up, unhappy, downward, down
[A]: unhappy


[Q]: prompt, water, current, delayed, do tests
[A]:
water