instruction:
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.
question:
Category: animal 
Words: fish, iguana, canyoning, hamster, horse
answer:
canyoning


question:
Category: construction 
Words: excavator, steam roller, concrete pourer, swallow, crane
answer:
swallow


question:
Category: elements 
Words: burn, combustion, sack, cool, fire
answer:

sack