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: dump truck, tackle, crane, duck, mallet

A: dump truck
****
Q: sergeant, lieutenant, fighter, general, ordinary

A: ordinary
****
Q: recruit, fire, earth, sack, instruct

A:
earth
****