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: current, history, wave, jetstream, whirlpool

A: history
****
Q: sergeant, general, standard, plain, ordinary

A: sergeant
****
Q: neighboring, close, nearer, out of service, on top of

A:
out of service
****