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: physical activity 
Words: drop, fall, leaves, bend, exercise
leaves

Category: outdoor sport activity 
Words: fish, hiking, row, shark, canoe
shark

Category: physical activity 
Words: autumn, run, climb, fall, roll

autumn